[CLONE] All user links should have rel="nofollow" attribute

This should be done in order to keep our Google Rating higher (proof links are appreciated). For example if user creates a post with link:

[url=http://jtalks.org]JTalks[/url]

On view page we should see:

<a href="http://jtalks.org" rel="nofollow">JTalks</a>

Acceptance Criteria:

• Links within the same domain should not have rel='nofollow'. Thus if user opens javatalks.ru and the link leads to http://javatalks.ru/topics/123 then it's not marked as nofollow.
• If user opens blah.javatalks.ru, then links like http://javatalks.ru/topics/123 should have nofollow attribute.
• If user opens javatalks.ru and link leads to wikipedia for instance, it should have nofollow attribute.

Pages to cover:

• User Profile (contacts, signature)
• Posts
• User Signature in posts