Updated Main Readme

Now includes the Spatial Understanding feature.

Author: Stephen Hodgson

README.md

@@ -9,9 +9,10 @@ HoloToolkit contains the following feature areas:
 1. [Input](Assets/HoloToolkit/Input/README.md)
 2. [Sharing](Assets/HoloToolkit/Sharing/README.md)
 3. [Spatial Mapping](Assets/HoloToolkit/SpatialMapping/README.md)
-4. [Spatial Sound](Assets/HoloToolkit/SpatialSound/README.md)
-5. [Utilities](Assets/HoloToolkit/Utilities/README.md)
-6. [Build](Assets/HoloToolkit/Build/README.md)
+4. [Spatial Understanding](Assets/HoloToolkit/SpatialUnderstanding/README.md)
+5. [Spatial Sound](Assets/HoloToolkit/SpatialSound/README.md)
+6. [Utilities](Assets/HoloToolkit/Utilities/README.md)
+7. [Build](Assets/HoloToolkit/Build/README.md)
 
 To learn more about individual HoloLens feature areas, please read the [Wiki](https://github.com/Microsoft/HoloToolkit-Unity/wiki) section.