Implement interface for JSON patch

[gpestana]

JSON patch creates and applies patches for JSON data structures. This library seems to be a good fit to provide a high-level interface for developers to use rdoc.

tasks

• Define API merging and manipulating rdoc structures
• Create and apply JSON merge (https://github.com/evanphx/json-patch#create-and-apply-a-merge-patch)
• Docs update + add examples