Added configuration option for rabbitmq deliveryMode. Basically it works
like a boolean, but having 1 and 2 as allowed values, we consider it
integer and validate it as such.
When sending a message, now we can tell rabbitmq which delivery mode we
want, according to main configuration option rabbitmq_delivery_mode
A small change in except syntax. This should make happy python3 and work
also in 2.6 and later.
Added documentation for rabbitmq_delivery_mode configuration parameter