Release 1.2.0

The pandoc-unicode-math filter now adds sensible whitespace where necessary: The Unicode sequence λx now translates to \lambda x (note the added whitespace) because the previous \lambdax would raise a Latex error, but αβ still translates to \alpha\beta because this is unambiguous. Idea by Fynn Leitow.

Several new symbols were added. Contributed by Fynn Leitow.