Merge pull request #128 from lisamuel/renameTimeline

Renamed Timeline to AnimationTimeline.
Fix missed rename
Merge pull request #129 from alancutter/targetConfigNamespace

Fix missed rename to webAnimationsTargetConfig in target-loader.js
Prefix all internal properties with _
Merge pull request #126 from dstockwell/prefix-internal

Prefix all internal properties with an underscore
Added getAnimationPlayers() to animation timeline.
Added getAnimationPlayers() to animatable elements.