Add support for options to publish and subscribe.
Extra parameter is optional.
memory and mqtt ascoltatores updated.
Test for memory ascoltatores, mqtt test needs to be done after mosca is updated to take advantage of the options (e.g. to pass the qos through).
Change use of __proto__ to Object.getPrototypeOf (former is ECMAScript 6 only).
Only support publish/subscribe through prototype
Don't inherit from AbstractAscoltatore in DecoratorAscoltatore.
It was causing a double 'ready' event emission.
Instead, make the functions to set up publish and subscribe methods available
to deriving classes and call them in DecoratorAscoltatore.
Merge pull request #55 from davedoesdev/pass_options_to_ascoltatores

Pass options to each Ascoltatore#publish and #subscribe