Added Slot#getIndex.

spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/SlotData.java

@@ -50,6 +50,10 @@ public class SlotData {
 		this.boneData = boneData;
 	}
 
+	public int getIndex () {
+		return index;
+	}
+
 	public String getName () {
 		return name;
 	}