code: public static synchronized void engage(Context context, String event, BooleanCallback callback) {
  		engage(context, event, callback, null, (ExtendedData[]) null);
  	}
docs: This method takes a unique event string, stores a record of that event having been visited,
  determines if there is an interaction that is able to run for this event, and then runs it. If
  more than one interaction can run, then the most appropriate interaction takes precedence. Only
  one interaction at most will run per invocation of this method. This task is performed
  asynchronously.
  
  @param context  The context from which to launch the Interaction. This should be an Activity,
  except in rare cases where you don't have access to one, in which case
  Apptentive Interactions will launch in a new task.
  @param event    A unique String representing the line this method is called on. For instance,
  you may want to have the ability to target interactions to run after the user
  uploads a file in your app. You may then call
  <strong><code>engage(context, "finished_upload");</code></strong>
  @param callback Called after we check to see if an Interaction should be displayed. Called with
  true if an Interaction will be displayed, else false.