Update the pie chart to use the default color/highlight if none is specified

Author: ds17f

src/Chart.Doughnut.js

@@ -92,6 +92,10 @@
 		},
 		addData : function(segment, atIndex, silent){
 			var index = atIndex !== undefined ? atIndex : this.segments.length;
+			if ( typeof(segment.color) === "undefined" ) {
+                segment.color = Chart.defaults.global.segmentColorDefault[index];
+                segment.highlight = Chart.defaults.global.segmentHighlightColorDefaults[index];				
+			}
 			this.segments.splice(index, 0, new this.SegmentArc({
 				value : segment.value,
 				outerRadius : (this.options.animateScale) ? 0 : this.outerRadius,