exponential backoff for failed messages

exponential backoff retry for failed messages
default settings = no retry delay - i.e., preserve legacy behavior
mvn deploy publishes artifacts to HBO archiva repository (http://maven.hurley.hbo.com:8000/repository/internal/ and http://maven.hurley.hbo.com:8000/repository/snapshots/)

See the following for an example how to use these changes:  https://github.com/HBOCodeLabs/Hurley-Cyclone/pull/207

switch back to public just in case there are storm or external systems that depend on this?  I agree it ought to be private.