message: Add notes for 0.5.4
diff: # Change Log
  +## 0.5.4
  +
  +Fix for [#806](https://github.com/howdyai/botkit/issues/806) - new version of websocket didn't play nice with Slack's message servers
  +
  +Support for Slack's new [rtm.connect method](https://api.slack.com/methods/rtm.connect).
  +
  +Use rtm.connect instead of rtm.start when connecting an RTM bot to Slack. This should performance during connections.
  +
  ## 0.5.3
  Add a new [readme file](readme.md) and moved other documentation into `docs/` folder.
  