derby updated to user bower

(#475)

This one was similar to the SocketStream example, #523. I created a .bowerrc to point to `/public/components`. That was about it for this one. I also tweaked the app a bit. It now:

* requires dblclick to edit,
* adds the "selected" class to the active view's footer link. I see this is working at `todomvc.derbyjs.com`, but wasn't working locally for me :-\
* re-structured the mark-up to conform to the normal template, which eliminated the need for an additional .css file.

As always, happy to make changes, and hope I didn't break anything :-D