auto_link should not create a link inside a link which has the rel attribute

auto_link gets confused when the a tag has something more than the href attribute and relinks inner html of the link

>> a = "<a href=\"http://google.gr\" rel=\"nofollow\">http://google.gr</a>"
=> "<a href=\"http://google.gr\" rel=\"nofollow\">http://google.gr</a>"
>> auto_link(a)
=> "<a href=\"http://google.gr\" rel=\"nofollow\"><a href=\"http://google.gr\">http://google.gr</a></a>"
>> auto_link(a.gsub(/\srel\="nofollow"/, ""))
=> "<a href=\"http://google.gr\">http://google.gr</a>"

sadly enough, I have fixed it locally but can't manage to submit a patch since I can't run the tests (and don't really have much time right now, might try to build a patch next week or something) but here is what seems like it helps a bit:

diff text_helper.rb  text_helper_modified.rb 
550c550
<             if left =~ /<[^>]+$/ && right =~ /^[^>]*>/
---
>             if (left =~ /<[^>]+$/ && right =~ /^[^>]*>/) || (left =~ /<a\b[^>]+>$/i && right =~ /^<\/a>/i)