0.12.1

• Fix CPP bug that prevented tests from building on Windows.
• Allow building with transformers-0.6.* and mtl-2.3.*. Because the
  MonadTrans t class gained a forall m. Monad m => Monad (t m) superclass
  in transformers-0.6.0.0, the MonadTrans and MonadTransControl instances
  for ActionT e now have a ScottyError e instance context to match the
  Monad instance.