hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-6-g5d5ccfe-dirty using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/7a2a9bbe1595c73f9aa2bba4c2a600c558ef5822
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/82f4bbff1b525f7cf33c525987268cdc651c3d33
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/831a37566be736e827a8f17d6c006a09ed384cd6
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/e7fd25c827f2a1bfb13ea6e716579b697a566ac3