Set nicer proctitles.

Having the entire path expanded in the proctitle can make it irritating
to debug what process is running when running a git-script. This way, we
end up with simpler commands such as `feature start new-feature` as
opposed to `/path/to/ruby feature start new-feature`.
Merge set-proctitles (#68) into master

Set nicer proctitles.

Having the entire path expanded in the proctitle can make it irritating
to debug what process is running when using a git-script. This way, we
end up with simpler commands such as `feature start new-feature` as
opposed to `/path/to/ruby feature start new-feature`.

Fixes #52.