Initial Appveyor support for testing IE11
Initial Appveyor support for testing IE11

AnalyticalGraphicsInc/cesium,jasonbeverage/cesium,YonatanKra/cesium,geoscan/cesium,YonatanKra/cesium,jasonbeverage/cesium,YonatanKra/cesium,progsung/cesium,soceur/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,soceur/cesium,kaktus40/cesium,CesiumGS/cesium,kaktus40/cesium,CesiumGS/cesium,josh-bernstein/cesium,progsung/cesium,CesiumGS/cesium,soceur/cesium,josh-bernstein/cesium,CesiumGS/cesium,geoscan/cesium,hodbauer/cesium,YonatanKra/cesium,likangning93/cesium,hodbauer/cesium,CesiumGS/cesium,hodbauer/cesium,AnalyticalGraphicsInc/cesium