Fixes #179

This is a partial revert of #126 using style from #176.

In #179, issue was identified where the recipient was nil in before callbacks on delivery methods. This fixes that issue and adds appropriate tests.

There were some other issues I identified while trying to increase test case coverage for callback methods, namely:

• Adding the following callback to CallbackExample in noticed_test would raise the argument error that recipient is nil, it is unclear if that is intended behavior:

before_deliver do
  raise ArgumentError unless recipient

  self.class.callbacks << :before_everything
end

• Adding an around_deliver callback to Noticed::DeliveryMethods::Test would fail multiple tests, as the #deliver method would not get called

• Adding before/around/after callbacks to CallbackExample on both everything and the database method would only call the everything callbacks, and not the method callbacks. For example, adding before_deliver and around_deliver callbacks to the example test would result in the test returning [:before_everything, :around_everything, :after_everything]

There's some unclear logic as to what callbacks get called when, and I'm not sure what is expected vs what happens in test vs what happens in an actual implementation, but happy to log to another issue or document elsewhere.