message: Update CHANGELOG with planned modifications
diff: ## HEAD
  +[Define canonical address callbacks](https://github.com/confio/cosmwasm/issues/73)
  +
  +* Use `&[u8]` for addresses in params
  +* Allow contracts to resolve human readable addresses (`&str`) in their json into a fixed-size binary representation
  +* Provide mocks for unit testing and integration tests
  +
  ## 0.5
  ### 0.5.2
  