Small bug (and fix) for text_helper.autolink

Hi,

ActionView::Helpers::TextHelper#autolink does not handle certain
mailto: links properly.

Assume the following html:
<a href="mailto:david@loudthinking.com">Mail me</a>

When running this html through autolink, it should not alter the html.
However it is transformed to:
<a href="mailto:<a
href="david@loudthinking.com">david@loudthinking.com</a>">Mail me</a>

I have created a ticket and added a patch:
http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1862-running-autolink-on-text-containing-a-mailto-link-breaks