Solved iss5 + updated bootstrap

Changes:
    - solved https://github.com/rosedu/events/issues/6
    - added error page to witch each error case links to
    - added bower, updated bootstrap to  3.3.1
    - added date-time picker in edit page
    - added link field for Event model that represents the external link for that event
    - added edit page link and email fields restrictions + various other changes