Return all known stats for a single node

[leotrs]

Currently, we have a way of seeing all attributes:

H.nodes.attrs[0]
# -> {"name": "Leo", "color": "green"}

What I'd love to have is a way of seeing all stats too:

H.nodes[0]
# -> {"degree": 10, "clustering": 0.5, "name": "Leo", "color": "green"}

This is assuming that stats are cached, and they will soon be as long as we have frozen hypergraphs (#50) ;)

[leotrs]

Related to #188 .

[leotrs]

Related to #405