Fix windows tempfile handling

On Windows, `ghc-mod lint` fails with following message.

    ghc-mod: DeleteFile "<Ommit>\\Temp\\ghc-mod-hlint8464": permission denied <Ommit>

Perhaps, On Windows, GHC opens file exclusively.
So, we move `removeFile` to `finally`.
Merge pull request #221 from satoshi-murakumo/fix-windows-tempfile-handling

Fix windows tempfile handling