Warn when version has not been specified in options

[dantman]

There is no good reason to make api calls without explicitly defining what version of the graph api you are using.

Whenever we plan to do the next major release with breaking changes we should add a warning.

The first time FB.api is called (or another method that uses the version) and version is not specified, we should emit a console.warn warning that the graph api version needs to be specified.

[thierryskoda]

👍

[simison]

Simply warning about it would not be breaking change, though?

Requiring specifying version would be.