Feature/parameterized colors

[benoitjadinon]

I've closed #3 by mistake but this time I nailed it, I fixed the precision issue, you were right @trentpiercy .

so I'm drawing strokes inside of the rect using oRect.deflate(rectPaint.strokeWidth/2)it's quite clean.

having Paints as parameters instead of colors, allows for customizing of the line size, color and style within one property, pretty awesome.

also added candleSpacing

            decreasePaint: new Paint()
              ..color = Colors.red
              ..strokeWidth = 1.0
              ..style = PaintingStyle.fill
            ,
            increasePaint: new Paint()
              ..color = Colors.green
              ..strokeWidth = 1.0
              ..style = PaintingStyle.fill
            ,
            volumePaint: new Paint()
              ..color = new Color.fromARGB(15, 255, 255, 255)
              ..style = PaintingStyle.fill,
            candleSpacing: 1.2,

default values are left as default (green stroke, red fill, volume same)