Specified start and end times for all events in dev_data to conform to model requirements
Merge branch 'master' into issue-60
Appropriate user permissions now required for creating and editing events and event groups.
loading dev_data now includes a group with these permissions and some test users who are and aren't members of the group.
Added a basic 403 template to which users are now taken if they attempt an action without permission.
Now redirects to login page if user isn't logged in