It is normal for boolean values, or predicates, to end with `-p' in
emacs-lisp, so `gac-automatically-push' should really be named
`gac-automatically-push-p'.
Add the ability to automatically push changes after commits. This just
calls `git push', so upstream and such should already have been set
up.
Setting `git-automatically-push' to `t' enables this functionality.
I refused to do this before because it reminds me too much of .Net's
Global Assembly Cache. Now I feel I need it, though, since
`git-auto-commit' is too long.
