Ensure proper working directory for fixup⇥ snippet

This is another command affected by the recent change of default working directory.
The diff views now highlight (added) trailing whitespace

Closes #12
Add git/config as possible file type.

Allowed per http://git-scm.com/docs/git-config#FILES.
Add proper escapes to unquoted string values

This fixes the issue in #16 where you may need to use a quote character without starting a quoted string context. Allowable escapes taken from http://git-scm.com/docs/git-config#FILES
Merge branch 'textmate'