Hierarchical graphs support

[jacomyal]

It would be nice to support hierarchical graphs in this parser. And the best would be to let the choice of the output, between data that are shaped as in the GEXF (ie. nodes stores in a tree), or as a nodes array with hierarchical edges between the related nodes (with a "hierarchy": "true" attribute, for instance).

[sftranna]

Any update? Looking for this

[Yomguithereal]

Hello @sftranna. This library is not very used anymore. We have migrated to this one instead. But I guess the issue here is to decide how to handle hierarchical graphs.