Don't ghc -prof on the Kitten executable

Cabal emits a warning:

> Warning: 'ghc-options: -prof' is not necessary and will
> lead to problems when used on a library. Use the configure
> flag --enable-library-profiling and/or
> --enable-executable-profiling.
Merge pull request #81 from strager/fix-prof

Don't ghc -prof on the Kitten executable