Add improvements to queues

[josephmancuso]

This adds an improvement to the queue drivers

You used to have to specify a job to pass through but now you can specify the callback on the fly or even specify a method directly:

class Something:

    def send(self):
        some_time_consuming_task()

and then run the queue:

def show(self, queue: Queue):
    queue.push(Something.send, args=('something', 'else'))

or specify a callback that should be used other than the handle method:

def show(self, queue: Queue):
    queue.push(Something, args=('something', 'else'), callback="send")

Not only will this allow us to queue random things on the fly but also allow certain things to be "queueable" like this:

class WelcomeEmail(..., ShouldQueue):
    ...

and then create new logic to queue it internally without having to pass it into the queue at all.

[coveralls]

Coverage decreased (-0.06%) to 89.79% when pulling 544dcc6 on add-improvements-to-queus into 8a8db0f on develop.