Some Git command line options are allowed to be repeated multiple times.
Examples of this are the -C flag which may occur more than once to
"strengthen" its effect, or the -L flag on Git blames, to select
multiple blocks of lines to blame.

    $ git diff -C -C HEAD~1 HEAD
    $ git blame -L 1-3 -L 12-18 HEAD -- somefile.py

This patch supports passing a list/tuple as the value part for kwargs,
so that the generated Git command contain the repeated options.

Popen defaults to using unbuffered reads, which are extremely slow.

Related to #383

Thanks travis, once again !

Fixes #383

We keep stdout closed, which seems to have the side-effect of
stdout being connected to your TTY, in case you run a terminal.

However, this shold also prevent deadlocks, as only stderr is used.
The alternative would have been to try to fetch lines concurrently,
and we have been there.

For clone(), `communicate()` is used, and with some luck this will
just do the right thing. Even though last time I checked, it
didn't ... ? Lets see.

Stab at #72

signal.SIGKILL is not available on Windows so use signal.SIGTERM as a backup
when SIGKILL is not available.

Include 'timeout' parameter in Git execute