Changelog for flat-0.4

Significant and compatibility-breaking changes. Version 0.4: - Compatibility with ghc 8.8.3 - Changed namespace from Data.Flat to Flat - Addtional Flat Instances for some common packages: array, base, bytestring, containers, dlist, text, unordered-containers, vector - Additional doctests, with a static version that can run without ghci and therefore also under ghcjs/eta (run it with stack test :doc-static) - Many minor changes Version 0.3.4: - Redisegned Generics-based instance generation (Data.Flat.Class) to reduce compilation time and improve encoding and decoding performance - Fixed GHCJS Double bug and tested GHCJS with full test suite Version 0.3.2: - Tested with ghc 8.2.1 - Dropped dependencies on the 'cpu', 'derive' and 'tasty' packages to make it compatible with the Eta compiler (https://github.com/typelead/eta) Version 0.3: - Removed 'flatStrict' and 'unflatStrict' (use 'flat' and 'unflat' instead that also encode/decode strictly) - `unflatWith` now takes a decoder for the unpadded value (previously it expected a padded decoder) and decodes the padded value - Added some decoding primitives - Added Data.ByteString.Convert