Send data to pebble using a "VirtualPebble" to avoid bluetooth errors

* send new message once the ack (or nack) of the precedent message is received
* can drop non-important messages if necessary
Merge branch '1.4' into 1.4_ImprovedAppMessage
v1.4.0-beta2
Merge pull request #16 from jay3/1.4_ImprovedAppMessage

1.4 improved app message