Shuffle that stack of monad transformers.

Running an OAuthM value will now always retain the (potentially)
modified Request.
Use parseOnly for parsing the oauth_timestamp param.
Fix non-exhaustive pattern match
Removing debug statements
Factor basic oauth validation into processOAuthRequest.

The various request processing that results in new secrets to be
generated use the processTokenCreationRequest function, which in itself
builds upon processOAuthRequest.
Adding Middleware function `withOAuth`
Simple travis file