Canvas methods enhance

How to use

1. get canvas ctx and add enhance methods to ctx

    var canvas = document.getElementById('canvas')
    var ctx = canvas.getContext('2d')
    ctx = new canvasHandle(ctx)

2. use provide methods

    ctx.strokeRoundRect(10,10,100,100,2,'#f00',[20,20,20,20])
    ctx.fillRoundRect(10,10,100,100,'#f00',[20,20,20,20])