cabal2nix.cabal: declare that we've been tested with GHC 7.6.1
cabal2nix.cabal: declare that we've been tested with GHC 7.6.1

gridaphobe/cabal2nix,spencerjanssen/cabal2nix,bennofs/cabal2nix,jb55/cabal2nix,Fuuzetsu/cabal2nix,psibi/cabal2nix,dmalikov/cabal2nix