[GuessTheNumber] Added Haskell program to create AES key.
[GuessTheNumber] Some improvements and changes for deployment.

In particular:
 * minor code improvements (remove debug output, unnecessary imports,
   clean up cabal file ...)
 * now use base 16 encoding instead of base 64 because the latter didn't
   work (generated 404 errors, I suspect some characters were not valid
   in the URL...)
 * some changes because of older bytestring-library version on server
 * implement guess history, output previous guesses
Merge branch 'master'