def parse(string)
      @stack = [ ParseContainerTag.new { |t| Utility.array_to_s(t.contents) } ]
      tokenize(string)
      stack_up
      @stack.last.to_s
    end
def parse(string)
      @stack = [ ParseContainerTag.new { |t| Utility.array_to_s(t.contents) } ]
      tokenize(string)
      stack_up
      @stack.last.to_s
    end
Creates a new parser object initialized with a Context.
 Parses string for tags, expands them, and returns the result.