Improve `git incoming` & `git outgoing` with overridable defaults.

Origin is the assumed default remote, unless $1 is provided, and the
current checked out branch is assumed as the default remote branch
unless $2 is provided. In other words, assuming we're on master:

    git incoming

would check `origin/master`, unless you provided:

    git incoming upstream pr-272

which would check `upstream/pr-272`.
Add Makefiles to .ackrc.
Remove `C-z z` in tmux.conf to allow for default zoom mode.

...which is more than awesome :)