trivial Docs.hs (generating docs.json missing " on type line)
Was a quote before the type value, but not after, leading to unhelpful error:
elm: Illegal unescaped character in string:
Fix cabal install missing docs.json
See: https://github.com/evancz/Elm/issues/120

Add build-hook to Setup.hs so that elm-doc gets build and executed before library or elm exec gets built.
Add preprocessor to Elm.cabal so LoadLibraries.hs can load docs.json from the build folder instead of installed folder
Add touch to Setup.hs otherwise LoadLibraries.hs doesn't get recompiled.  This is non-portable, but I can't find a portable way (see Setup.hs for details)

cabal clean && cabal install now works
(tested on ghc 7.4.1)
Merge pull request #122 from ngunn/dev

Dev (fix cabal install as per issue 120)