Implement custom view did finish animating for step view controllers

[syoung-smallwisdom]

RSDTaskViewController presents step view controllers using a UIPageViewController. Because the page view controller fires the viewDidAppear method before the animation is finished, any UI actions handled in the step view controller's viewDidAppear method must use a 0.3 seconds delay to give transitions and animations time to complete.

Replace the page view controller with a custom implementation of a page view that handles firing this transition message correctly.