Re-organize files and namespaces
Don't use double quote for strings when it's not needed
Test the controller directly instead of using Session#projects
Fix test description
Move the find logic from ProjectsController#find to Project::find
Remove extraneous RedStack::Access class
Define a project#users method

There are now two types of controllers here: object controllers
(user_controller, project_controller) and array controllers
(users_controller, projects_controller). This is meant to avoid models
(user, project) from knowing about controllers.