Document interface for OP-based CRDT JSON

This release ships the mechanics barebones for Conflict-free replicated JSON implementation in Go based on Martin Kleppmann, Alastair R. Beresford work.

At this point, rdoc implements a document interface for an operation-based CRDT JSON data structure.

Features

• Create new CRDT JSON document using the document API;
• Manually create operations to mutate the document locally;
• Apply local operation using the document API;
• Apply remote operation using the document API;