Improve CesiumTerrainProvider tests.
Revert changes to viewExtent. Move check for zero vector sooner and adjust if needed.
Update CHANGES.md.
Fix onDataSourceRemoved, and move onDataSourceChanged.
Fix duration for animations with count = 1
Temp workaround for glTF issue 219
Merge pull request #1420 from AnalyticalGraphicsInc/meshTerrain

Add support for mesh terrain tilesets like those produced by STK Terrain Server
Viewer can now track which data source has the active clock.
Fix CHANGES.md
Fix JSHint warning
Merge remote-tracking branch 'origin/master' into gltf
Merge branch 'master' into dynamicScene-refactor
Fix developer error when zooming creates an invalid frustum. Also fix crash when attempting to normalize the zero vector during translation in 2D.
Merge branch 'master' into cameraZoom2D

Conflicts:
	CHANGES.md
Merge branch 'master' into viewExtent

Conflicts:
	CHANGES.md
Start of model tests
Add renderForSpecs
Added new model for testing
Picking and other new tests
Removed DeveloperError doc for required parameters