created a sessions controller with minimal corresponding view and Rspec tests
added signin form (w/o create action ready for submit)
passed Rspec test for invalid log-in info (with correct error message being displayed -- exactly persists until a 'request' is made
added create_remember_token and related methods to make it work
added implementation of sign_in() so now can succefully sign-in && changed header and added drop_down menu once login
We can now sign out