URL normalizing, more options for gender & custom website links

A couple changes to make the site respect the Account page more:

 - When updating profile, add `http://` to urls which don't begin with `http://` or `https://`. This lets us `href` directly to the URL on file without any filtering necessary. (useful for the next item)
 - When viewing news items by a particular submitter, change the username link to point to their website if specified in their account settings. Otherwise, link to their Github.
 - Allow a user to specify "other" or "unspecified" gender.

I am happy to rebase the branch if necessary.