Implement ILookUp and clojure.lang.Associative for TitanElements

[ZackGC]

This would give us some crazy super powers, as seen on stack overflow

Particularly the following

(:age (v/create! {:age 1))
;;1 
(:age (assoc (v/create! {:age 1}) :age 10))
;;10
(:age (update-in (v/create! {:age 1}) [:age] inc))
2

Not sure we can or should do Associative, but ILookUp definitely.