Add hooks for some recipes

- Add ac-ghc-mod
- Rewrite from elpa rainbow and sunrise-commander
- Fix sclang-snippets
There is a potential future issue with this.  Let's say `company-mode` or some other auto-completion framework decides to support auto-complete sources, if a user wants to use `ac-ghc-mod` with such a framework they may or may not have `ac-sources` defined and they would definately not want `auto-complete-mode` to be set.