twitter-screen-name Extract a twitter screen name from a twitter URL or @username string. Return null if not valid. Example var twitterScreenName = require('twitter-screen-name') twitterScreenName('http://twitter.com/_alanshaw') // -> _alanshawtwitterScreenName('https://www.twitter.com/_alanshaw') // -> _alanshawtwitterScreenName('http://twitter.com/_alanshaw/status/695527644901801984') // -> _alanshawtwitterScreenName('@_alanshaw') // -> _alanshawtwitterScreenName('_alanshaw') // -> _alanshaw// etc. twitterScreenName('http://example.org/foo/') // -> nulltwitterScreenName('toolongfortwitter') // -> null// etc.