Add hi2 recipe

HI2 is a new cleaned up indentation mode for haskell-mode.

I'm the maintained and author of the package.

Official package repository is the github repository: http://github.com/errge/hi2

I can be reached via the issue tracker on github or at gergely@risko.hu

License is GPLv3, because the haskell-indentation-mode that I based the work on was already licensed with GPLv3.