Mod1

Couple new features added.

1) self.search_by_title method and its implementation to search in header
2) recent_videos method and its implementation in category show
3) sign_in, sign_out, register and root routes as user resources
4) add bcrypt gem, add bootstrap_form gem
5) add current_user and logged_in? methods to application controller and their helper_methods
6) require_user in all 'internal_pages'
7) redirect root and sign in urls if user is logged in to home

Please, approve.