Fixed broken 'Contact Us' link

The very first link on this page is broken.

old: http://openhatch.readthedocs.org/en/latest/contributor/contact.html
new: http://openhatch.readthedocs.org/en/latest/community/contact.html

I have verified the that the new link is correct and working as intended.
Merge pull request #266 from younjin/patch-2

Fixed broken 'Contact Us' link