Update README for new feature.
Add a connection type.

Having this type will be useful for the next step which involves adding
more complex toplogies.
Implement Url() method on connection struct.
Refactor defaults to be less verbose.
Start implementing multiple queue handling.

Start extracting configuration reading into a set of structs, that
uses topology as the top most element. This new type will act as
storage for the configuration data confining the dependency on
the conf module to one place.
Get parsing a single queue/exchange working

Next up handling multiple queues and exchanges needs to work.
Add tests for configuring multiple queues + exchanges.
Add tests for unmatched queues + exchanges.
Update consumer to use multiple queues/exchanges.

A separate goroutine is used to run each consumer to make things run
faster.