Use CCBatchNode properly.

In the previous code, the error usages of CCBatchNode are:
1. CCBatchNode is created from daisy-texture.png, while sprites are created from daisy.png. There's no relations between sprites and batchNode.
2. You add both batchNode and sprites as children of parent node. But the correct usage is to 
(1) parent->addChild(batchNode)
(2) batchNode->addChild(sprite)
(3) This line breaks the batchNode optimisation: parent->addChild(sprite)

I added the particle number from 700 to 2000, batchNode speed up the process correctly on my ipad2. You can have a try.