Add a slight delay to the Navigation Drawer flow

Add a slight (currently 300ms) delay to the Navigation Drawer flow,
enabling the animation to run smoothly before we start opening a
new activity or displaying a new fragment.

Note: Assignments lock up the UI for some non-apparent reason. That
needs to be resolved. :-)
Merge pull request #148 from ninetwozero/project-app-butter-1

Add a slight delay to the Navigation Drawer flow