Define event models.

https://github.com/madewithbytes/us_ignite/issues/102

The events have a publishing workflow, the mandatory
fields are::
  - Name
  - Venue
  - User that submitted the application
Add event detail page.

https://github.com/madewithbytes/us_ignite/issues/103

Once an ``Event`` has been published the URL is available
for everyone to see.
Updated model, added helper methods for an event.
Add visibility method for an ``Event``.

https://github.com/madewithbytes/us_ignite/issues/103

``is_visible_by`` will determine if the user provided
can view the given ``Event`` this is determined by
publication or ownership.
Allow the event owner to preview the draft version.

https://github.com/madewithbytes/us_ignite/issues/103

The view will show the event to the owner of the
event even if it is in ``DRAFT`` mode.
Add admin section for the ``Events``.

Useful for monitor and debug.
Add ``Event`` details to the view.

https://github.com/madewithbytes/us_ignite/issues/103