message: Format migration guide
diff: @@ -23,7 +23,8 @@ Integration tests:
  All Tests:
  -All usages of `mock_env` will have to remove the first argument (no need of API).
  +All usages of `mock_env` will have to remove the first argument (no need of
  +API).
  ```rust
  // before
  @@ -35,9 +36,9 @@ let env = mock_env("creator", &coins(1000, "earth"));
  Contracts:
  -* All code that uses `message.sender` or `contract.address` should deal with
  - `HumanAddr` not `CanonicalAddr`. Many times this means you can remove
  - a conversion step.
  +- All code that uses `message.sender` or `contract.address` should deal with
  + `HumanAddr` not `CanonicalAddr`. Many times this means you can remove a
  + conversion step.
  ## 0.8 -> 0.9
  