[bin/git-ol] Rewrite, totes way better

Makes this much faster, better argument handling: if first arg starts
with - all args are passed to git log, otherwise first arg is used as
upstream and others are passed to git log. Upstream defaults to @{u}.

Ex:

    git ol
    # Branch has no upstream, specify
    git ol origin/master

    # Patches touching FIXMEs
    git ol -SFIXME
    # With no upstream
    git ol origin/master -SFIXME

    # Branch starts with - for some insane reason
    git ol jk you're screwed