Changelog for gray-code-0.3.1

0.3.1: revert API to be backwards compatible with 0.2.2, requires GHC >= 7.8 0.3: DON'T USE THIS VERSION. rely on total functions on `FiniteBits`, requires GHC >= 7.8 0.2.2: build on GHC 7.6, integrate tests with cabal build 0.2.1: `toList'` function 0.2: split `C.B.G.Bits` and `C.B.G.List` APIs 0.1: initial Hackage release