refactor example app (remove canvas example)
remove support for canvas app flow
cleanup readme. update old links. remove old info.
some more README.md updates
Update example's Gemfile.lock.
add a note about skipping omniauth CSRF
remove a derp
Rescue `NoAuthorizationCodeError` in callback_phase
Add tests when authorization code is not included in callback
Prepare 2.0.0.pre1