Update for hapi v6.  Hapi error handling.  Hapi authentication.

I've brought this plugin up to date so that it's usable with hapi v6.  I've overhauled error handling so that errors go through Boom and get processed by hapi (setting status codes, headers, etc in a way that's more "native" to hapi).  I expose the Token and Authorization error objects differently.  I grab user info from the hapi auth credentials object so that authentication can be used natively in hapi.  There's still work to be done, particularly in the documentation and in applying settings to oauth2orize.  And there's yet more to do on the error-handling end.  But we have some usable code!