0.5.1 Version

This version introduce the following features :

• messaging :
  • Add the option to turn off link unfurling
• support of new events :
  • User change events (see: https://api.slack.com/events/user_change)
  • Pin added / removed events (see: https://api.slack.com/events/pin_added / https://api.slack.com/events/pin_removed)
• bug fixes :
  • isOk() in ParsedSlackReply is difficult to use (#39)
  • ClassCastException thrown when using openMultipartyDirectMessageChannel (#42)
  • ChannelHistoryModule always get blank (#49)
  • Need to cast explicitly a SlackReply to use it due to a glitch in reply parser (#41)