Added callback redirection support for public authenticator

The new API wrapper is quite well written and straight forward to integrate with however it didn't support the callback redirection required by my app. I have made these changes and have successfully processed the callback redirection.
Ideally there should be a sample web app to demonstrate the integration but I didn't attempt to include it. Hopefully later releases will include an example. 
In my case I just used my app to test end to end oAuth including call back redirection step.