Adding realtime to explore mode.
Merge pull request #293 from mithro/simple-realtime

Basic "real time" mode (previous called "manual" mode)
Add a test that keyframe property values are stringified
Merge pull request #338 from steveblock/keyframeToString

Add a test that keyframe property values are stringified
Implemented pauseAnimationsForTesting and test-pause-for-testing.
Merge pull request #336 from rjwright/pauseForTesting

Implemented pauseAnimationsForTesting + test.
Remove handling of zero property-specific keyframes

This case should never occur.
Add test for type of Animation.effect when created with a keyframe dictionary
Handle null property values in keyframes

Also add a test that invalid property values are ignored
Don't add composite or neutral as CSS properties of KeyframeInternal

Also add a couple of asserts for compositing.
Merge pull request #339 from steveblock/keyframeFixes

A few minor tweaks and bug fixes for KeyframeAnimationEffect
Implement accumulate for KeyframeAnimationEffect