Updates to splines from splines branch.
Merge branch 'master' into splines2
Merge branch 'master' into splines2
Merge branch 'master' into splines2

Conflicts:
	Source/Core/CatmullRomSpline.js
	Source/Core/HermiteSpline.js
	Source/Core/LinearSpline.js
	Source/Core/QuaternionSpline.js
	Specs/Core/CatmullRomSplineSpec.js
	Specs/Core/HermiteSplineSpec.js
	Specs/Core/LinearSplineSpec.js
	Specs/Core/QuaternionSplineSpec.js
Updates after merge.
Tweak CHANGES.md
Make Viewer.trackedObject an observable.

Removed `Viewer.objectTracked` event which is no longer needed.
Merge pull request #1404 from AnalyticalGraphicsInc/viewer-trackedObject

Make Viewer.trackedObject an observable.
Merge pull request #1362 from AnalyticalGraphicsInc/splines2

Splines 2
Fix failing specs by properly isolating and cleaning up animations.

Each AnimationCollection instance now manages its own list of animations.  Previously all instances would share global state.  Also upgrade Tween to latest version.
Merge pull request #1408 from AnalyticalGraphicsInc/fixAnimationSpecs

Fix failing specs by properly isolating and cleaning up animations.
Merge branch 'master' into particles