Merged fd leaks fix from the master to the 0.3 version

Ensure consistent output from git command

Fix the `git version` parser.

GitRunCommand exception can store stdout output too.

(cherry picked from commit ca2b901e7229fc5c793762fd4e4c1c38c5a78e80)

Some git commands, like git merge outputs their problems onto stdout,
instead of stderr, which will be thrown away by the current setup. This
change allows the GitPython commands to store the stdout's value too,
in case of error.

The git command output can vary by language which would cause assertions
errors when parsing the output.

On POSIX system the language used by git can be adjusted by LC_MESSAGES.
The special language 'C' is guaranteed to be always available and is
whatever default the software has been written in (usually english, the
case for git).

Thus passing LC_MESSAGES to Popen will ensure we receive from git a
consistent output regardless of the user preference.

Addresses #153

Add __call__ method to Git object to allow
passing git command options to the executable
requires flag to transform_kwargs
add unit test

Change-Id: If1bc01008e66d3fd3811c15b56e58f38c95b9887

Add __call__ method to Git object to allow
passing git command options to the executable

Change-Id: If1bc01008e66d3fd3811c15b56e58f38c95b9887