Solves #138.
* Removed user and user_roles from fixture
* Restricted user creation to one user. That user is id 1, is admin
* Changed tests so they accommodate for this fact
* Can not create new user (fails on test, flashes on signup)
- Created Role model
- Created Permission model
- Linked Users->Roles with a belongsToMany relationship
- Linked Permissions to Users and Roles with a belongsToMany relationship
- Created permissions helper with functions for initializing and
checking permissions (canThis)
- Unit tests for lots of things