Uses HscNothing and falls back to HscInterpreted if necessary (#205)

Two Test case are fails but it is not fatal.

Language/Haskell/GhcMod/Check.hs

@@ -34,8 +34,7 @@ check :: IOish m
       => [FilePath]  -- ^ The target files.
       -> GhcModT m (Either String String)
 check fileNames = do
-  withLogger setAllWaringFlags $ do
-    setTargetFiles fileNames
+  withLogger setAllWaringFlags $ setTargetFiles fileNames
 
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