v0.8.4

Fixed bugs:

• Connect whilst suspended does not appear to be connecting immediately #167
• Prep for 0.9 spec #145

Closed issues:

• RSC11: Environment option #160
• ably-java 0..8.3 release isn't available on jcenter #155

Merged pull requests:

• issues/170: Fixed message serial out of sync after recover #175 (trenouf)
• heartbeat support #173 (trenouf)
• tpr/issue167: Fixed explicit connect after connection has disconnected #172 (trenouf)