* fix opentsdb emitter always be running
* check if emitter started
* add more details about consumeDelay in doc
* fix possible thread unsafe
* fix fail sending tags whose value contain colon
* opentsdb emitter extension
* doc for opentsdb emitter extension
* update opentsdb emitter doc
* add the ms unit to the constant name
* add a configurable event limit
* fix version to 0.13.0-SNAPSHOT
* using a thread to consume metric event
* rename method and parameter