add a test for ListWrapNode in TC_HtmlFormat
replaced ListWrapNodeFormatter and EnumWwrapNodeFormatter with ListLeafNodeFormatter
defined HtmlFormat::HeadingNodeFormatter#make_html_element to assign the name of its heading element as a value of class attribute
introduced HtmlElement#configure
use HtmlElement#configure to tidy up HeadingNodeFormatter, HeadingLeafFormatter and ListLeafNodeFormatter
some tidying ups
Merge branch 'develop' into 2html
add an option for including the table of contents in a generated html
assign the value of OPTIONS[:css] to a local variable "css" so that it can be refered in templates
make @head accessible from HtmlTemplate#head
in HtmlElement: make style elements rendered properly
Merge branch 'develop' into 2html