Add history.js module to track user reading trends
Merge branch 'master' into reading-storage
Leave trailing slash on short URL's being stoed in history
Ensure short URLs can only be persisted to localStorage history
Raname history array 'shift' to 'queueJump' method to be more consise
Ensure history module handles change in history maxSize
Use common error abstraction to throw error
Merge pull request #2165 from guardian/reading-storage

User reading history