handle border, resolve tsayen#44

apply background color styles to whole canvas

add toJpeg function, by @stefanogithub

support style rendering option

support width and height options

support browserify, by @maciejdzikowicki

render to pixel data, by @andystanton

do not fail rendering when request timeout occurs

do not apply filter to the root node

fix tsayen#24: if an element is an SVG <rect>, copy its width and hei…

…ght attributes to style