Merge pull request #8 from dualface/develop

merge the official update
Merge pull request #261 from zrong/develop

Add filters and some new features.
Merge pull request #11 from dualface/develop

merge the update
enhancement:draw a circle at the position we give

## enhancement:draw a circle at the position we give
之前的drawCircle的位置默认是（0，0）点，只能通过node的位置来调整，画圆时应该可以指定圆心的位置
Merge pull request #1 from dabing1022/ChildhoodAndyDev

谢谢！

但我认为 pos不应该是第一个参数才对。它应该放到后面的参数组中。