added current_user and logged_in? helper methods.  Created nav bar in layout header, that displays link to home at all times and profile and logout links if logged in
change user create action to directly render the homepage(login) when authentication fails, had to change the sign up form not to use an instantiated user(user variable)
modified spec_helper and added sessions controller tests
- modified spec_helper to whipe test database using DatabaseCleaner gem after all tests
- added 3 tests for sessions controller (2 for login, 1 for logout)
- GREEN all test passing
added routes, model, migration and needed associations for questions