v0.23.0

• Use an unique id (shortid) for server-level messageId.
  #176.
• Removed node-uuid in favor of shortid.
• Bumped browserify to v4.2.0.
• Allow persistence.factory key to be a string in the configuration/options
  #171.
• Do not store inflight packets on disconnection
  #175.
• Send suback 0x80 if a subscription fails
  #170.
• Moved pre-commit into devDependencies.
  #177.

Thanks to Morgan Cheng for all the work
spent to make Mosca rock solid on Redis.