diff --git a/.document b/.document
deleted file mode 100644
index ecf3673..0000000
--- a/.document
+++ /dev/null
@@ -1,5 +0,0 @@
-README.rdoc
-lib/**/*.rb
-bin/*
-features/**/*.feature
-LICENSE
diff --git a/LICENSE b/LICENSE
index 7e831f5..804de3a 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2009, 2010, 2011, José Pablo Fernández
+Copyright © 2009, 2010, 2011, José Pablo Fernández
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1a3faba
--- /dev/null
+++ b/README.md
@@ -0,0 +1,54 @@
+assert_difference
+=================
+
+A nice assert_difference method similar to the one provided by Rails but with
+some improvements. For example:
+
+    assert_difference "Company.count" => +1, "User.count" => +5, "Slot.count" => -1 do
+      post :something
+    end
+
+will assert that a company and 5 users were create (the plus sign is only for
+the visual aid) and a slot was removed.
+
+[Rails' assert_difference](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_difference)
+would require a more verbose syntax:
+
+    assert_difference "Company.count" do
+      assert_difference "User.count", +5 do
+        assert_difference "Article.count", -1 do
+          post :something
+        end
+      end
+    end
+
+To use it with Test::Unit add this code (untested, please
+[let me know](mailto:pupeno@pupeno.com) if it works):
+
+    class Test::Unit::TestCase
+      include Factory::Syntax::Methods
+    end
+
+and to use it with RSpec:
+
+    RSpec.configure do |config|
+      config.include Factory::Syntax::Methods
+    end
+
+For more information read http://pupeno.com/blog/better-assert-difference
+
+Note on Patches/Pull Requests
+-----------------------------
+
+* Fork the project.
+* Make your feature addition or bug fix.
+* Add tests for it. This is important so I don't break it in a
+  future version unintentionally.
+* Commit, do not mess with rakefile, version, or history.
+  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
+* Send me a pull request. Bonus points for topic branches.
+
+Copyright
+---------
+
+Copyright (c) 2010, 2011, José Pablo Fernández. See LICENSE for details.
diff --git a/README.rdoc b/README.rdoc
deleted file mode 100644
index 03a5527..0000000
--- a/README.rdoc
+++ /dev/null
@@ -1,34 +0,0 @@
-= assert_difference
-
-Better assert_difference than Rails by providing a more compact and readable
-syntax through hashes. Instead of writing:
-
-    assert_difference "Article.count" do
-      assert_difference "assigns(:article).comments(:reload).size" do
-        assert_difference "Article.count", -1 do
-          post :something
-        end
-      end
-    end
-
-you can *now* write:
-
-    assert_difference "Article.count" => 1, "assigns(:article).comments(:reload).size" => 1, "Article.count" => -1 do
-      post :something
-    end
-
-For some more information read http://pupeno.com/blog/better-assert-difference
-
-== Note on Patches/Pull Requests
-
-* Fork the project.
-* Make your feature addition or bug fix.
-* Add tests for it. This is important so I don't break it in a
-  future version unintentionally.
-* Commit, do not mess with rakefile, version, or history.
-  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
-* Send me a pull request. Bonus points for topic branches.
-
-== Copyright
-
-Copyright (c) 2010, 2011, José Pablo Fernández. See LICENSE for details.
diff --git a/Rakefile b/Rakefile
index b0b1527..144a269 100644
--- a/Rakefile
+++ b/Rakefile
@@ -21,4 +21,9 @@ Rcov::RcovTask.new do |test|
 end
 
 require "yard"
-YARD::Rake::YardocTask.new
+YARD::Rake::YardocTask.new do |yard|
+  # Use Markdown for documentation.
+  yard.options << "--markup" << "markdown"
+  # Extra file(s).
+  yard.options << "-" << "LICENSE"
+end
diff --git a/assert_difference.gemspec b/assert_difference.gemspec
index 45542ab..b6cab8e 100644
--- a/assert_difference.gemspec
+++ b/assert_difference.gemspec
@@ -2,7 +2,7 @@
 # Copyright © 2011, José Pablo Fernández
 
 $:.unshift File.expand_path("../lib", __FILE__)
-require "assert_difference/version"
+require "assert_difference"
 
 Gem::Specification.new do |s|
   s.name = "assert_difference"
diff --git a/lib/assert_difference.rb b/lib/assert_difference.rb
index 3c03771..e6554b8 100644
--- a/lib/assert_difference.rb
+++ b/lib/assert_difference.rb
@@ -1,4 +1,77 @@
-# Copyright © 2011, José Pablo Fernández
+# -*- encoding: utf-8 -*-
+# Copyright © 2010, 2011, José Pablo Fernández
 
-require "assert_difference/version"
-require "assert_difference/assert_difference"
+module AssertDifference
+  VERSION = "0.3.0" unless defined?(::AssertDifference::VERSION)
+
+  # Test numeric difference between the return value of an expression as a result of what is evaluated
+  # in the yielded block.
+  #
+  #     assert_difference "Article.count" do
+  #       post :create, :article => {...}
+  #     end
+  #
+  # An arbitrary expression is passed in and evaluated.
+  #
+  #     assert_difference "assigns(:article).comments(:reload).size" do
+  #       post :create, :comment => {...}
+  #     end
+  #
+  # An arbitrary positive or negative difference can be specified. The default is +1.
+  #
+  #     assert_difference "Article.count", -1 do
+  #       post :delete, :id => ...
+  #     end
+  #
+  # An array of expressions can also be passed in and evaluated.
+  #
+  #     assert_difference [ "Article.count", "Post.count" ], +2 do
+  #       post :create, :article => {...}
+  #     end
+  #
+  # A error message can be specified.
+  #
+  #     assert_difference "Article.count", -1, "An Article should be destroyed" do
+  #       post :delete, :id => ...
+  #     end
+  #
+  # Various assertions can be combined into one, instead of writing:
+  #
+  #     assert_difference "Company.count" do
+  #       assert_difference "User.count", +5 do
+  #         assert_difference "Article.count", -1 do
+  #           post :something
+  #         end
+  #       end
+  #     end
+  #
+  # you can *now* write:
+  #
+  #     assert_difference "Article.count" => 1, "assigns(:article).comments(:reload).size" => 1, "Article.count" => -1 do
+  #       post :something
+  #     end
+  #
+  # @param [Array, Hash] expressions array of expressions to evaluate or hash
+  #   table of expressions and expected difference.
+  # @param [Integer] difference expected difference when using an array or single expression.
+  # @param [String, nil] message error message to display. One would be constructed if nil.
+  def assert_difference(expressions, difference = 1, message = nil, &block)
+    b = block.send(:binding)
+    if !expressions.is_a? Hash
+      exps = Array.wrap(expressions)
+      expressions = {}
+      exps.each { |e| expressions[e] = difference }
+    end
+
+    before = {}
+    expressions.each { |exp, _| before[exp] = eval(exp, b) }
+
+    yield
+
+    expressions.each do |exp, diff|
+      error = "#{exp.inspect} didn't change by #{diff}"
+      error = "#{message}.\n#{error}" if message
+      assert_equal(before[exp] + diff, eval(exp, b), error)
+    end
+  end
+end
diff --git a/lib/assert_difference/assert_difference.rb b/lib/assert_difference/assert_difference.rb
deleted file mode 100644
index 4b6ee7d..0000000
--- a/lib/assert_difference/assert_difference.rb
+++ /dev/null
@@ -1,69 +0,0 @@
-# Copyright © 2010, 2011, José Pablo Fernández
-
-module AssertDifference
-  # Test numeric difference between the return value of an expression as a result of what is evaluated
-  # in the yielded block.
-  #
-  #   assert_difference "Article.count" do
-  #     post :create, :article => {...}
-  #   end
-  #
-  # An arbitrary expression is passed in and evaluated.
-  #
-  #   assert_difference "assigns(:article).comments(:reload).size" do
-  #     post :create, :comment => {...}
-  #   end
-  #
-  # An arbitrary positive or negative difference can be specified. The default is +1.
-  #
-  #   assert_difference "Article.count", -1 do
-  #     post :delete, :id => ...
-  #   end
-  #
-  # An array of expressions can also be passed in and evaluated.
-  #
-  #   assert_difference [ "Article.count", "Post.count" ], +2 do
-  #     post :create, :article => {...}
-  #   end
-  #
-  # A error message can be specified.
-  #
-  #   assert_difference "Article.count", -1, "An Article should be destroyed" do
-  #     post :delete, :id => ...
-  #   end
-  #
-  # Various assertions can be combined into one, instead of writing:
-  #
-  #   assert_difference "Article.count" do
-  #     assert_difference "assigns(:article).comments(:reload).size" do
-  #       assert_difference "Article.count", -1 do
-  #         post :something
-  #       end
-  #     end
-  #   end
-  #
-  # you can *now* write:
-  #
-  #   assert_difference "Article.count" => 1, "assigns(:article).comments(:reload).size" => 1, "Article.count" => -1 do
-  #     post :something
-  #   end
-  def assert_difference(expressions, difference = 1, message = nil, &block)
-    b = block.send(:binding)
-    if !expressions.is_a? Hash
-      exps = Array.wrap(expressions)
-      expressions = {}
-      exps.each { |e| expressions[e] = difference }
-    end
-
-    before = {}
-    expressions.each { |exp, _| before[exp] = eval(exp, b) }
-
-    yield
-
-    expressions.each do |exp, diff|
-      error = "#{exp.inspect} didn't change by #{diff}"
-      error = "#{message}.\n#{error}" if message
-      assert_equal(before[exp] + diff, eval(exp, b), error)
-    end
-  end
-end
diff --git a/lib/assert_difference/version.rb b/lib/assert_difference/version.rb
deleted file mode 100644
index 8a40ea0..0000000
--- a/lib/assert_difference/version.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-# -*- encoding: utf-8 -*-
-# Copyright © 2011, José Pablo Fernández
-
-module AssertDifference
-  VERSION = "0.3.0" unless defined?(::AssertDifference::VERSION)
-end