def initialize(text = nil, options={})
      super(RichTextRun)
      add_run(text, options) unless text.nil?
      yield self if block_given?
    end
creates a new RichText collection
@param [String] text -optional The text to use in creating the first RichTextRun
@param [Object] options -optional The options to use in creating the first RichTextRun
@yield [RichText] self