Add rendering by DIV capability.

I've added a function to generate the QR code using DIV.  I did this because I have performance issue when converting the resulting HTML to PDF using wkhtmltopdf when I use table rendering and faced difficulties in getting a consistent output from wkhtmltopdf if I choose canvas rendering.  Rendering using DIV is the easy way out for me.  PDF generation using wkhtmltopdf requires half of that using table and I do not have to tweak the HTML or wkhtmltopdf flag to achieve the consistent result.