Rename wai-oauth to oauth-provider
cabal file cleanup
Require empty token for one-legged authentication.
Better response error for 'emptyTokenLookup'
More haddocks.
Make OAuthT less general, fixing the Reader environment type parameter.

It doesn't seem like the environment parameter of ReaderT really needs
to be kept open. Therefore, the type alias OAuthM was removed and
OAuthT renamed to OAuthM.