Converted over to using dropwizard-protobuf

* Removed internal code for supporting protocol buffers
* Removed dropwizard-asset bundle and attempt at creating API documentation (never really worked)
* Upgraded the newrelic-api from 3.7.2 to 3.9.0
* Don't hardcode "User-Agent" everywhere, use a constant
Merge pull request #12 from jplock/jp-protobuf

Converted over to using dropwizard-protobuf