v.next Add twitter anywhere library

[timwingfield]

Add the twitter anywhere library to add "connect with twitter" functionality.

https://dev.twitter.com/docs/anywhere/welcome

Once this is in place, we should be able to use callbacks to capture who tweeted and the tweet id. Saving those along with the location they clicked the button from (console.log in location_view.js.coffee) to the database should get us started on the check-in feature.