added TableNodeFormatter#deep_copy_tree(). tree should remains unaffected after being visited.
added an option "strict_mode".
removed the parameter "gfm_conformant" from TableNodeFormatter#format_table() and use @options.gfm_conformant instead.
In TableNodeFormatter#visit(), use #create_self_element() instead of Node.new
introduced TableNodeFormatter#format_table()
changed the place of PlainTextFormat#get_plain() and #format()
refactoring of MarkDownFormat#format()
changed the place of the definition of class NotConformantStyleError
changed the default parameter value of MarkDownFormat.create()
introduced MarkDownFormat#push_visited_results()
introduced TableNodeFormatter#choose_expander_of_col_and_row
MarkDownFormat::TableNodeFormatter inherits PlainTextFormat::TableNodeFormatter
introduced VerbatimNodeFormatter#gfm_verbatim()
introduced VerbatimNodeFormatter#md_verbatim()
add an option: :gfm_style => false.
fixed a bug: tables in html are not properly formatted.
add an option: :gfm_style => :force and cleaned up TableNodeFormatter#format_table().
add a blank line after tables converted into html
update pseudohikiparser.gemspec and Rakefile