Add Google Maps API scripts

Generated a Google Maps API key.  Included this and the necessary links in helper methods,
which are used in the application.html.erb header.
Create main controller for realtime map.

Generated the controller used to display and control the realtime map.  Updated
routes.rb to reflect that this is the main page.
Simple canvas and support for display of map.

Updated the homepage to include a canvas for the Google map itself.  Added simple
code in map.js.coffee to load this map to verify that the Google maps API is
working properly.