Fix 138: allow xgi.draw to set color of individual nodes or edges

[leotrs]

See #138. Also see attached image, ran from this branch.

[mcontisc]

This works, yes. However, it still gives problem when you pass an array because the access for arrays is also through node id and not through node position.

[nwlandry]

How about accepting a list or array and mapping indices to nodes like this? (In addition to the dictionary and string methods)

# colors is an input array
nodes = list(H.nodes)
color_dict = {nodes[i]: colors[i] for i in range(H.num_nodes)}

a more succinct way to do that would be color_dict = dict(zip(H.nodes, colors)). This would index the nodes sequentially by the order in which they were added.

[leotrs]

@nwlandry I actually don't like that one because it would effectively be like accepting a de-facto second node ID. The user can already access the node addition order by just looping over H.nodes.

Wait actually I think I misunderstood what you said. You mean accepting an array like @mcontisc is suggesting, and assuming the order of the colors in the array is the same as the node-addition order, correct? In that case, then yes that's what I was thinking.

[leotrs]

Done! Now xgi.draw accepts str, dict, or any iterable. If an iterable, the order of the colors in the iterable is assumed to be the same as the order of the nodes in H.nodes. I believe this is what @nwlandry was suggesting, no?

[mcontisc]

Yes, I agree :) Thanks a lot!
Out of curiosity, this is not possible for the hyperedges right? I mean, for coloring them we can only use a colormap. Correct?

[leotrs]

For now, yes. It would be nice to have a way to override the color assigned to a hyperedge via some other parameter, cc @iaciac.

[nwlandry]

Looks great!! I think it's ready to merge! I can add the coloring individual edges as an issue.