(#16, #17) automatically create default company

* Gon and Capybara gems
* remove old unused file from app/assets/javascripts/lib/
* add user_interactions layout
* add Setup class
* add setups resource, controller, view show error message for users if github configs not found
* move welcome/signin to sessions/new
* move gitlab settings from ENV to DB
* add rake task github_gitlab_configs:from_env_to_default_company
* move "Manage Projects" button to navbar
* let users to sign in to default company only by using github
* let admins to see their company settings
* fix associations
* fix migrations and fix tests
* add first feature tests