Created sessions controller and integration tests.
Implemented initial routes, controller methods and view for signing so that integration tests will passl.
Created tests for sign in.
Created signing form.
Started fleshing out the create method for session (login).
Updated session create method to handle invalid logins, updated tests
Created a remember_token for signed in users (to maintain state). Updated tests.
Implemented sign_in method.
Set our current_user instance variable to allow sessions across pages.
Added html to nav for signed in users, updated helpers.
Fixed syntax error in digest method (User model).
Completed implementation for signing in users, updated tests.
Implemented sign out, updated tests.