https://doc.rust-lang.org/nightly/std/collections/hash_map/enum.Entry.html <img width="655" alt="screen shot 2016-08-28 at 8 18 17 pm" src="https://cloud.githubusercontent.com/assets/416575/18039971/cdf181bc-6d5c-11e6-90c1-0354f269e702.png">
