expand tabs to spaces should be similar to Text::Tabs::expand

Source Code

# File action_mailer/vendor/text-format-0.6.3/text/format.rb, line 698
def __expand(to_expand) #:nodoc:
  expanded = []
  to_expand.split("\n").each { |te| expanded << te.gsub(/\t/, ' ' * @tabstop) }
  expanded.join('')
end