Parses URLs of social networks to extract IDs or screen names.
It does not get confused by child routes: you may also pass URLs like a user's twitter photo stream and the gem will extract their twitter ID .
Note that it just parses URLs, and does nothing magic like looking up IDs when the URL contains only a screen name (e.g. the Instagram API requires you to send the user ID almost always while you at first only know their screen name).