Add test helpers

[BrianSipple]

Ongoing idea list:

• assertCurrentTour(assert, tourName) {}
• assertTourActive(assert, message = 'tour is active) {}
• assertTourInactive(assert, message = 'no tour is active') {}
• assertTourStep(assert, stepName) {}
• assertTourStepHidden(assert, message = 'tour is active but current step is not shown') {}
• assertTourStepVisible(assert, message = 'tour is active and current step is shown') {}

[grapho]

I support this idea, though perhaps exposing Shepherd's modalContainer would allow tours to render inside of the actual app and therefore could be tested in acceptance tests and possibly allow for visual regression tests (Percy)

[RobbieTheWagner]

@grapho I responded to this in the other issue, but responding here as well. All Shepherd options can be used in ember-shepherd, without the need to expose extra things. You would have to pass these options as part of your tour/steps config, like the other options.

Also, Ember's test helpers take a parent element, so you are not limited to the Ember testing container, and you can still write tests here.