added basic user authorization

@RichardBlair 
Updated routing, controllers, and views in adding user authentication to dickbook to match Rails 4.1.1 standards utilizing information from the following resources:

http://railscasts.com/episodes/250-authentication-from-scratch
https://github.com/rails/strong_parameters
and, of course, advice from https://github.com/RichardBlair
This makes it so if I did this:

```
class BoardsControllers < SessionController

end
```

every controller action in BoardsController would require the user to log in.