Fix Gemfile; run migrations in Travis

* Show Travis badge in README
* Make cache dir before starting
* Remove duplicates in Gemfile
Merge pull request #12 from swalberg/master

Fix Travis CI build
Added user authentication via devise and adjusted previous RSpec tests to be devise friendly.
Fixed user login redirect feature tests
Added user nav menu, fixed HTML validity issues, added nav tests
Added missing database_cleaner gem
Added devise helpers, added login before calling the methods in the controller
Moved the login helpers to a separate file under support, added log_me_in in the features in the before block
Merge branch 'f9_add_user_signup_and_login'