Use div for integral division on tileChunk.

> quickCheck $ \n -> floor ((fromIntegral n :: Double) / 16) == n `div` 16
+++ OK, passed 100 tests.
Remove trailing whitespace from all modules.
Move all Haskell source code files to new directory src/.
Add Cabal file.

  $ cabal configure
  $ cabal build
Avoid the need for FlexibleInstances language extension.
Avoid unnecessary use of GADTs.
Add support for Haddock.

In order to build the Haddocks for the executable, use

  $ cabal configure
  $ cabal haddock --executables --internal
  $ gnome-open dist/doc/html/Minehack/Minehack/index.html