Completed ContinuousPushViewController

- For ease of unit testing, included accessibilityLabel with subviews
with the exception of the label which gets its own accessibilityLabel
as a matter of course.

- Added Continuous Push + Collision to examples_table_controller

- Cleaned up InstantaneousPushViewController code

- Added spec tests for ContinuousPushViewController
Merge branch 'continuous_push_view'