Update editable model logic to allow members.

https://github.com/madewithbytes/us_ignite/issues/121

The membership model contains detail when a user can
edit a given ``Application``.
Allow members with edit permissions to update application.

https://github.com/madewithbytes/us_ignite/issues/121

The edit view of the application allows the members
with permissions to update the details.

The validation occurs in the ``Application`` model where
ownership or write permissions are validated.