Adds description to CHANGES.md
Adds description to CHANGES.md

likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,YonatanKra/cesium,YonatanKra/cesium,YonatanKra/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,progsung/cesium,progsung/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,YonatanKra/cesium