fix #149 began decoupling scene graph draw and buffer graph draw logic. This will enable more flexibility for developers to define custom buffer draw functions, and it also improves draw performance for both the scene and buffer graphs, because each function can be optimized for its purpose. Also moved text drawing logic to the Text shape

src/shapes/Sprite.js

@@ -19,6 +19,7 @@ Kinetic.Sprite.prototype = {
         });
 		this.shapeType = "Sprite";
         config.drawFunc = this.drawFunc;
+        config.drawBufferFunc = this.drawBufferFunc;
         // call super constructor
         Kinetic.Shape.call(this, config);
         this.anim = new Kinetic.Animation();
@@ -48,6 +49,17 @@ Kinetic.Sprite.prototype = {
             this.drawImage(context, this.attrs.image, f.x, f.y, f.width, f.height, 0, 0, f.width, f.height);
         }
     },
+    drawBufferFunc: function(context) {
+        var anim = this.attrs.animation;
+        var index = this.attrs.index;
+        var f = this.attrs.animations[anim][index];
+
+        context.beginPath();
+        context.rect(0, 0, f.width, f.height);
+        context.closePath();
+        this.fill(context);
+        this.stroke(context);
+    },
     /**
      * start sprite animation
      * @name start