Support `viewBox` attribute in `svg` tag

[fmaylinch]

I don't know much about SVG format but at SVGParser:1001 the code looks for attributes width and height while I used this SVG file which has a viewBox attribute with those measures.

So, I changed that code with:

        if (localName.equals("svg")) {

            Float w = getFloatAttr("width", atts);
            Float h = getFloatAttr("height", atts);

            if (w == null || h == null)
            {
                String vb = getStringAttr("viewBox", atts);
                if (vb == null) {
                    throw new RuntimeException("Can't find size attributes: width+height or viewBox");
                }
                String[] measures = vb.split(" ");
                w = Float.parseFloat(measures[2]);
                h = Float.parseFloat(measures[3]);
            }

            int width = (int) Math.ceil(w);
            int height = (int) Math.ceil(h);

            canvas = picture.beginRecording(width, height);

Thanks for the lib!