Merge pull request #10 from chead/feature/9_linear_user_flow

Linear user-flow. Switched MainViewController from UIViewController to U...
Merge pull request #11 from chead/feature/8_cancel_authorization_button

Added UINavigationController and cancel button for authorization view.
Fixes #12 and #13.
Merge pull request #14 from chead/feature/13_12_web_view_size_and_keyboard

Fixes #12 and #13.