Merge pull request #213 from hagbarddenstore/master

Updated RabbitMQ to 3.2.1.
updated changelog
fixed Rabbit transport nuspec + updated Rabbit package dep in test project
Changed bacckoff behavior to be configurable

* Enabled configuration of the backoff helper on the worker threads.

* Renamed the IConfigureAdditionalBehavior.cs file to
  ConfigureAdditionalBehavior.cs to follow the type matches filename convention.