Added SvgPathImage which renders whole QR code as one path

Rendering QR code as path removes white spaces which may occur when zooming
the SVG image. See http://i41.tinypic.com/s5im9c.png
Python 2.6+ compatibility
Merge pull request #37 from hareevs/master

Added SvgPathImage which renders whole QR code as one path
svg_path: add test and make code work on py25
More shortcut factories for qr script
Add some SVG factories that fill the background white