Fix conditional notifiers

* The `ConditionalNotifierDeclaration#compile` method instantiates
  an instance of the notifier, so do not try and `new` the
  instance again.
* Update specs to reflect what the `ConditionalNotifierDeclaration#compile`
  method is doing behind the scenes.
Merge pull request #19 from czarneckid/fixing-conditional-notifiers

Fix conditional notifiers, by removing double instantiation attempt