Merge pull request #144 from RasaHQ/prepare-1.7.0-release

Changed

• ReminderScheduled and ReminderCancelled now take intent and entities
  as options, instead of action. This is because starting with Rasa 1.7 reminders
  trigger intents (with entities) instead of actions.
• The following FormAction methods are now async by default: validate_slots,
  validate, submit and run. User-defined classes inheriting from
  FormAction should be adapted to use async for these methods. Existing
  synchronous implementations will continue to work as normal, but this behaviour will
  be deprecated in the future.
• The following ActionQueryKnowledgeBase methods are now async:
  utter_objects and run.
• The following KnowledgeBase methods are now async:
  get_attributes_of_object, get_key_attribute_of_object,
  get_representation_function_of_object, get_objects and get_object. Same
  warning for FormAction applies here - user-defined classes should be updated to
  use async, but will continue to work for the moment.
• The following InMemoryKnowledgeBase methods are now async:
  get_attributes_of_object, get_objects and get_object.