Add helpers for getting the line / column of a region

I couldn't find these built in for emacs. Weird.

Also, one of the tests (the one for the end column) fails for me on the
first try. The second try works. I don't have the energy to figure out
why. :|
Implement extracting a method from the currently selected text

Both emacs and evil mode selections should be supported now
Add "extract method" to README
Merge branch 'feature-extract-method' into develop
Document the OmniSharpServer version on which this relies

This is the minimum version on the server side.
This should be updated whenever there is a change to omnisharp-emacs
that requires a newer version of OmniSharpServer.