Lightweight library for JSON graph

Library, similar to:

https://github.com/jsongraph/jsongraph.py

NB: json-graph-lite library uses list for nodes, not object, so it's not compatible with JSON Graph Format.

JSON Graph Format compatible classes (Graph, Graphs) can be found from json_graph_lite.jgf.

Incompatible change: list is used for nodes, not object, because JSON object can't represent integer keys.

The intention of json-graph-lite is to provide lightweight graph library, which serializes and deserializes graphs a la JSON graph format.

Take a look at tests/test_graphs.py for usage examples.