Add automatic variable highlighting to grammar.

This pull request includes:

* Highlighting of Powershell bitwise operators.
* More comparison operators like `-match` and `like`.
* Removal of Python language variables.
* Addition of automatic variables in Powershell which are highlighted as `variable.language` rather than `variable.other`. More information about automatic variables can be found [here](http://technet.microsoft.com/en-us/library/hh847768.aspx).
* Refactoring of tests for automatic variables.

I have unintentionally included the two previous "prepare release" commits by rebasing from `origin` instead of `upstream` but I think that these should be merged automatically (I hope). 
i think it would be a good idea to include a CSON of automatic variables that we can just pull into the tests and iterate through. It would be simpler to add keywords as test cases and reduce some of the boilerplate from testing the Automatic variables. Mind trying that out?

It might be a good foundation (or model) for future additions to follow as well.