added HTML5 doctype to output, unfortunately xml.etree.ElementTree provides no nice way of doing so.
added proper support for figure, figcaption. legend is now skipped as there is no equivalent html5 element.
colgroup and col are not of much use in conversion from RST. There is no
RST syntax to change their attributes, nor is there any attributes you
would really want to modify. In any case, styling is CSS's job.
Merge pull request #26 from russkel/doctype

added HTML5 doctype to output
Merge pull request #28 from russkel/removecoltags

remove col group
Merge pull request #29 from russkel/figure

Figure support
fix incorrect placement of header and footer elements
put section titles into header elements