pickle support for the GraphiteReporter

This is based on https://github.com/BrightcoveOS/metrics-graphite-pickle but refactored for
metrics 3.
update failures on exception
prefer protected over package private
Merge branch 'master' into graphite-pickle

Conflicts:
	metrics-graphite/pom.xml
	metrics-graphite/src/main/java/com/codahale/metrics/graphite/Graphite.java
Pickled graphite improvements
Persistent connections to graphite
Formatting fix
Flush graphite after report, also verify close on stop
Defer resolution of hostname supplied to Graphite

Somewhat difficult with UDP, as I don't want to re-resolve on every
single call to 'send'.
Reformatted
Merge pull request #639 from dropwizard/graphite-pickle

GraphiteReporter improvements