introduced a helper function TC_HtmlFormat#convert_text_to_html
properly ignores CommentOutNode in a html generated with HtmlFormat
merged xhtml-visitor
introduced HtmlFormat::CommentOutNodeFormatter
introduced ListLeafNode, ListTypeLeaf, ListWrapNode and EnumWrapNode
removed XhtmlFormat::Formatter[HeadingLeaf].make_html_element that is unnecessary now
reordered the sequence of class definitions
implemented ListLeafNode#breakable? and ListTypeLeaf#push_self
now list items can be converted into li elements properly
introduced HtmlFormat::LinkNodeFormatter
add tests for links in xhtml