Add and connect jquery, underscore, and backbone

* Downloaded the compressed versions of jquery, underscore and backbone
* Added template inheritance as per http://flask.pocoo.org/docs/patterns/templateinheritance/
* Renamed app folder to static folder, as flask by default searches the
  static folder for any files loaded with url_for
* At this point, the files are hooked up.
* My next step is to create a backbone view that will display a map of SF