add -z flag to tar

IHaskell.cabal

@@ -101,7 +101,7 @@ executable IHaskell
   hs-source-dirs:      src
   main-is:             Main.hs
 
-  build-tools:         happy
+  build-tools:         happy, cpphs
   
   -- Modules included in this executable, other than Main.
   other-modules:       

ipython-kernel/ipython-kernel.cabal

@@ -23,7 +23,6 @@ library
                        IPython.Message.Parser
                        IPython.Message.UUID
   -- other-modules:       
-  build-tools:         cpphs
   other-extensions:    OverloadedStrings
   hs-source-dirs:      src
   default-language:    Haskell2010

src/IHaskell/IPython.hs

@@ -197,7 +197,7 @@ installPipDependencies = withTmpDir $ \tmpDir ->
 
       -- Extract it.
       cd tmpDir
-      run_ tarPath ["-xf", versioned ++ ".tar.gz"]
+      run_ tarPath ["-xzf", versioned ++ ".tar.gz"]
 
       -- Install it.
       cd $ fromText versioned