Fix upcoming Git 2.0 breaking change to `git add -A`.
Ensure C locale is used when processing command output

This change makes sure LC_MESSAGES is set to C whenever command output
is run through grep, sed etc. Otherwise aliasing will fail whenever
localized messages are printed.

This should fix #98 and #64.
Merge pull request #137 from ilkka/master

Ensure C locale is used when processing command output
Merge pull request #131 from chasballew/git_add_all_deprecation_fix

Fix upcoming Git 2.0 breaking change to `git add -A`.