Ctags (Vi) format

TODO:

* Add tests (figure out how to get vi to output filename & line number
  to stdout, for integration tests).
* Sort the tags?
Properly reference the python2 executable

See here: http://legacy.python.org/dev/peps/pep-0394/
Ignore symlinks
Change comment that breaks vim highlighting
Sketch of assert_vim
Add some vim tests

This commit adds assert_vim tests to some of the existing tests that
call assert_emacs.
Add a few more vim tests

To match all the emacs integration tests.
Merge branch 'vim-support'

* vim-support:
  Add a few more vim tests
  Add some vim tests
  Sketch of assert_vim
  Change comment that breaks vim highlighting
  Ignore symlinks
  Properly reference the python2 executable
  Ctags (Vi) format