CausalBase Serialization

[bobby]

Currently, it is possible to view the EDN current-state of a CausalBase. However, there is no way to serialize the entire CausalBase (including history, etc.) for, e.g., putting it in LocalStorage in a browser or sending it on the wire.

CausalBase should implement the CLJ(S) multimethods and protocols necessary to serialize its entirety to EDN, and should add EDN readers for de-serializing back into memory.

Transit would also be nice to have, but could be maintained as a separate project, to keep dependencies lean and clean.