[ue4] Implemented two color tinting.

CHANGELOG.md

@@ -65,7 +65,8 @@
  * Fixed renderer to work with 3.6 changes
  * Added new UPROPERTY to SpineSkeletonRendererComponent called `Color`. This allows to set the tint color of the skeleton in the editor, C++ and Blueprints. Under the hood, the `spSkeleton->color` will be set on every tick of the renderer component.
  * Added support for clipping.
- * Switched from built-in ProceduralMeshComponent to RuntimeMeshComponent by Koderz (https://github.com/Koderz/UE4RuntimeMeshComponent, MIT). Needed for more flexibility regarding vertex format, should not have an impact on existing code/assets.
+ * Switched from built-in ProceduralMeshComponent to RuntimeMeshComponent by Koderz (https://github.com/Koderz/UE4RuntimeMeshComponent, MIT). Needed for more flexibility regarding vertex format, should not have an impact on existing code/assets. You need to copy the RuntimeMeshComponentPlugin from our repository in `spine-ue4\Plugins\` to your project as well!
+ * Added support for two color tinting. All base materials, e.g. SpineUnlitNormalMaterial, now do proper two color tinting. No material parameters have changed.
 
 ## C#
  * **Breaking changes**