Removes old commented code that is not longer needed.
Adds bare bones Group resource and associated CRUD.

Introduces the Group model. It is intended to be used to categorize
Users. This will allow for Users that are on the same team to
see each other's Tickets and access each other's uploaded Attachments.

This only implements the Group resource and the corresponding dashboard CRUD.
Adding access control restrictions for the Group associations will come
next, along with a dashboard mechanism for actually assigning the Users
to Groups.
Removes rspec mock() deprecation warnings by switching to double()
Adds access controls vis-a-vis Groups.

Standard Users are now able to access Tickets belonging to other
members of their group as well as any Attachments other group members
have uploaded.
Adds dashboard User CRUD.

Project managers are now able to CRUD Users in the dash and associate
them with Groups. This is a very simple first implementation and doesn't
do anything regarding mailing new Users their credentials or any other niceties.