Graphlib

Prior to 0.9.3 traversal of outgoing relationships from a node were supported. Now incoming relationships can be created and traversed with any node.

- `match_props` and `update_props` can now be passed into the `Node` and `Rel` constructor
- class attributes still exist, however this makes it simpler to work with per instance
- Add support for the [array-based format](https://github.com/bruth/json-graph-specarray-based-format) of the JSON Graph Spec which is not the default output from the serializer
- The class attribute `reltype` (from ac35f5f2) has been renamed to `relclass` to have it not be confused with the `type` attribute on `Rel` instances.
- The serializer has been refactored to use a stack instead of recursion to prevent `MaximumRecursionDepth` exceptions for very long relationships.
- A Neo4j parser and loader has been included
- This was migrated from the example script in the JSON Graph Spec repository. This has been heavily refactored and improved on.

The `Node.relate` method defines a new relationship with another node. Prior to this release, the `Rel` class was fixed, but now the `Node.reltype` can be set to a custom `Rel` class.

The 0.9 release denotes the first public release with tentative API changes based on public use.