Merge pull request #7 from telser/purescript-0.8-warnings

Fix warnings generated by purescript-0.8.0

Author: garyb

src/Control/Monad/Eff/Ref.purs

@@ -6,7 +6,7 @@
 -- | local scope.
 module Control.Monad.Eff.Ref where
 
-import Prelude
+import Prelude (Unit, unit)
 import Control.Monad.Eff (Eff())
 
 -- | The effect associated with the use of global mutable variables.

src/Control/Monad/Eff/Ref/Unsafe.purs

@@ -3,7 +3,7 @@
 module Control.Monad.Eff.Ref.Unsafe where
 
 import Control.Monad.Eff (Eff())
-import Control.Monad.Eff.Ref
+import Control.Monad.Eff.Ref (REF)
 import Control.Monad.Eff.Unsafe (unsafeInterleaveEff)
 
 -- | This handler function unsafely removes the `Ref` effect from an