Remove sleeps from the Cucumber tests

[dnrce]

wait_until is probably the source of some brittleness.

Defined in features/support/tracks_step_helper.rb.

[dnrce]

wait_for_animations_to_end should also be completely unnecessary.

[dnrce]

sleep still exists in a number of places.

[dnrce]

Partially addressed in 4830cc0.