port to gofer 2.1.

Updated to work with gofer 2.1.  Latest upstream and in Fedora 21.
- improved support for multiple messaging adapters (formerly transports).
- standardized url which includes messaging adapter.  format: *adapter*+*scheme*://*user*:*password*@*host*:*port*/*virtual-host*  instead of the *transport* option.
- hundreds of new unit tests.
The *transport* terminology renamed to *adapter* and still needs to be specified since the pulp gofer plugin assembles the url using information from consumer.conf.