bowling: Improve Haskell style

I tried to find some common ground between a couple of Haskell style
guides and the Prelude source. HLint's advice was also useful.

  Prelude: http://www.haskell.org/onlinereport/standard-prelude.html
  HLint: http://community.haskell.org/~ndm/hlint/
  style guides:
    http://www.haskell.org/haskellwiki/Programming_guidelines
    https://github.com/tibbe/haskell-style-guide/blob/master/haskell-style.md
    http://snapframework.com/docs/style-guide
Merge branch 'bowling'