def tagify input
      output = input.dup
      raise StandardError, "@tags is empty!" if @tags.empty? #improve on this
      @tags.each {|key,value| output.gsub!(tag_start.to_s+key.to_s+tag_end.to_s, value.to_s)}
      return output
    end
def tagify input
      output = input.dup
      raise StandardError, "@tags is empty!" if @tags.empty? #improve on this
      @tags.each {|key,value| output.gsub!(tag_start.to_s+key.to_s+tag_end.to_s, value.to_s)}
      return output
    end
Tagifies the supplied input.

 @param [String] input The string to tagify.
 @raise [StandardError] @tags must not be empty.
 @return A string with the tags replaced with their values.