color support, page context, c2d updates

http://htmlpreview.github.io/?https://github.com/Flamenco/jsPDF/blob/master/test/test_from_html.html

http://htmlpreview.github.io/?https://github.com/Flamenco/jsPDF/blob/master/test/test_context2d.html

from_html link works from Firefox, not Chrome...

We should consolidate the CSS color code into another plugin.  I copied it from c2d for now.