redirect-based oauth2 flow

- authorize after redirect
- Use localStorage to save userState before redirecting to Google OAuth2
- put gapi mock to repo gapi-mock
- Redirect-based google oauth 2 auth
- works with gapi-mock
- move fixture data to gapi-mock repo
- remove observer on gapi fake db as the responsibility of persistance is now shifted to gapi-mock
- make rv-gapi-mock a dev-only dependency