Adding support for multiple selection/update

[geryogam]

Thank you Stefan for this amazing Python implementation of the JSON Patch specification. RFC editor's Mark Nottingham is gathering ideas for a revision of the specification (JSON Patch 2). There is a key feature that JSON Pointer and JSON Patch are missing in my opinion: support for multiple selection/update. What do you think of my proposal? I would be awesome to see that implemented in your JSON Pointer and JSON Patch Python modules: json-patch/json-patch2#23