int -> long
performance improvements:
     - fit as many messages (that are in the queue) into the MTU as possible
     - convert to NIO

In addition to any NIO improvements,
     this will offer a performance improvement when the incoming message rate per the time it takes to call blockingSend() goes above one.

Add NonBlockingStatsDClientPerfTest to ensure no messages are lost in a concurrent environment.
Merge pull request #7 from finn-no/feature/automatic-multi-metrics

performance improvements: squash messages, and NIO
Merge pull reqest #9 making api take longs since they will end up just being strings. Testing against dogstatsd shows that it can parse longs
restores compatibility with vanilla statsd
 references:
  statsd documentation – https://github.com/etsy/statsd/blob/master/docs/metric_types.md
  breakage from commit dcae  – https://github.com/indeedeng/java-dogstatsd-client/commit/dcaed45c36ef74ba370d806647a4a06b173a9566#commitcomment-5832637