added htmlformat.rb
moved the definition of class HtmlFormat into htmlformat.rb
a tidy-up of HtmlFormat
moved test cases for HtmlFormat into test_htmlformat.rb
removed unnecessary blank lines
a clean-up for a consistent coding style
deleted an unused function
a clean-up of HtmlFormat for a consistent coding style
a clean-up of BlockParser for a consistent coding style
a clean-up of InlineParser for a consistent coding style