Add support for pushing and committing

I'm one of those strange people who edits their symlinks instead of doing the usual DVCS workflow on their dotfiles repo. These commits allow one to type `ghar commit` to have a `git add` and a `git commit` done with a banal message in the `-m` argument to `git commit`. Typing `ghar push` pushes any commits, though I believe the main reason it works for me is that I am in X11 with OpenSSH's X11 passphrase prompter. Finally, typing `ghar cap` ("cap" being short for "**c**ommit **a**nd **p**ush") does both of the above, in order, while being smart enough to do the second only if the first succeeded.