publish: redo oauth dance when publishing interactively

[snarfed]

we already do this when you try to disable listen or publish for your account, so it shouldn't be too hard to add to the publish interactive UI. background in irc.

cc @aaronpk, @tantek

[snarfed]

todo:

• nonce to prevent double submission (already handled by existing code that prevents double publishing)
• check that authed user is actually the user that's publishing (heh)
• re-render full user page in response
• twitter
• instagram
• only allow publishing from the user whose page you're on
• tests
• make error toast messages red instead of yellow