[TORQUE-1033] Create messaging objects with a default :encoding

This allows to specify default encoding when creating a queue or topic:

TorqueBox::Messaging::Queue.start("/queues/one", :encoding => :edn)
TorqueBox::Messaging::Topic.new("/topics/one", :encoding => :edn)
Merge pull request #140 from goldmann/TORQUE-1033-default-message-encoding

[TORQUE-1033] Create messaging objects with a default :encoding