A user can create, view, add listings to, and view the listings of a gro...

...up

  *The pictures of all users in that group are displayed at the top
  *The name of the user who added the listing is displayed along with its url
  *Group join invitations and routing are implemented but untested and are likely to be buggy

  TODO:
    *Push to heroku
    *Force facebook to crawl our join page so that our join links, when shared, will appear as valid. [See this reference](http://stackoverflow.com/questions/17982183/facebook-fb-ui-send-dialog-intermittently-returns-invalid-link-error/18055274#18055274)
    *Fix rack-flash so that it can be implemented without throwing errors