Remove the data-default dependency

ghc-mod.cabal

@@ -160,7 +160,6 @@ Executable ghc-mod
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
                       , async
-                      , data-default
                       , directory
                       , filepath
                       , pretty

src/GHCMod.hs

@@ -8,7 +8,6 @@ import Control.Applicative
 import Control.Monad
 import Data.Typeable (Typeable)
 import Data.Version (showVersion)
-import Data.Default
 import Data.List
 import Data.List.Split
 import Data.Char (isSpace)
@@ -303,9 +302,6 @@ data InteractiveOptions = InteractiveOptions {
       ghcModExtensions :: Bool
     }
 
-instance Default InteractiveOptions where
-    def = InteractiveOptions False
-
 handler :: IO a -> IO a
 handler = flip catches $
           [ Handler $ \(FatalError msg) -> exitError msg