Add Reader functionality into postlude.

postlude.cabal

@@ -18,4 +18,5 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   build-depends:       base >= 4.7 && < 5,
-                       mtl == 2.2.1
+                       mtl == 2.2.1,
+                       transformers == 0.5.2.0

src/Postlude.hs

@@ -36,12 +36,23 @@ import Control.Monad as X
   , return
   )
 
+import Control.Monad.Reader as X
+  ( MonadReader
+  , ask
+  , local
+  , reader
+  )
+
 import Control.Monad.Trans as X
   ( MonadIO
   , lift
   , liftIO
   )
 
+import Control.Monad.Trans.Reader as X
+  ( ReaderT (..)
+  )
+
 import Data.Bool as X
   ( Bool(..)
   )