Test that styles and timing are visible after a player seek
Repeat the last tick at last tick time when active animation state changes.

This includes changes to:

 * Players which have ticked at least once.
 * The animation tree (including changing the source of a Player)
 * Specified timings

A repeat is not triggered by changes to AnimationEffects.
Rename Animation.animationEffect to effect and use a bool in exitModifyCurrentAnimationState
Make depth counting exception safe
Test chaning player start time
Use timed_test API
More explanation and checks for animation state tracking
Merge pull request #267 from dstockwell/test-update-state

Repeat ticks when animation state changes