Remove the timeout and use async.map and Array.reduce

This set of commits does two things:

First it adds "use strict"; to index.js and fixes the code to work with that.  All javascript should be written using "use strict" to avoid painful and hard to debug errors.

Second, it replaces the timeout and for loop to score tweets with async.map and then computes the final score using Array.reduce.  Map-reduce, look at that :)

Let me know if you have any questions.