Log Message:
Update net/ruby-amqp to 0.6.7.

No changelog published; from the commit history:

* Allow :no_declare=>true on new Exchanges to prevent sending Exchange.Declare
* Add MQ::Queue#purge (thanks Uwe Kubosch)
* Avoid opts.delete() to prevent issues during reconnect and wrapper apis that \ 
pass in options
* Add MQ#recover to redeliver unackd messages
* Add :confirm => some_proc for Queue#subscribe to receive ConsumeOk
* Make rpc return queues autodelete
* Re-send prefetch command on reconnect
* Stop adding to the load path, use File.expand_path instead
* Remove a queue from MQ#queues on CancelOk if it is autodelete