publish: check for rel-me link to silo on signup

[snarfed]

if it's not there, complain but still allow it since they can add it later.

[snarfed]

i could also use this in the mf2 handlers to determine whether to use the web site from the user's profile or the profile URL itself in the served h-card.

thanks to @aaronpk for the idea: http://indiewebcamp.com/irc/2014-03-19/line/1395250363

[tantek]

Should be reasonably straightforward to do a quick check of the website URL to see if it has a rel=me link back to the Twitter profile URL, and if so, use the website URL. Simpler than looking for an h-card etc.

[snarfed]

obsolete, closing.