make_slug.rb

    def make_slug(str)
      return if str.blank? or !str.instance_of? String
      s = str
      s.downcase!
      s.strip!
      s.gsub!(/[^a-z0-9\s-]/, '') # Remove non-word characters
      s.gsub!(/\s+/, '-')     # Convert whitespaces to dashes
      s.gsub!(/-\z/, '')      # Remove trailing dashes
      s.gsub!(/-+/, '-')      # get rid of double-dashes
      s.to_s
    end