User reading history

This is a simple JS module that tracks user reading history and persists to localStorage.

It currently stores the last 100 read articles, keyed by their shortUrl in local storage. The next steps will be to persist this data through to Identity against their Guardian profile. 

We also would like to track the top n sections a user visits.

/cc @indeox according to Matt this may be of use to the work your doing as well?

!['Packing'](http://sprinklesinsprings.com/wp-content/uploads/2011/08/packing-gif-small1.gif)