
- has_cycle: return the cycle as a list of vertices
- Better graph viewer and editor
- Improve the website
- It should be possible to specify the first vertex to visit in traversal
  algorithm (suggestion of Fabrice Derepas)
- Implementations for graph with unlabeled vertices
  (exactly like graph with unlabeled edges)
- Provide more bidirectional graph implementation:
  only Imperative.Digraph.ConcreteBidirectional exists at this day.
- Provide generic marks (instead of only integer marks)

## DGraph

### mode Tree

- texte trop bas
- texte multi-ligne
- gros zoom déviant
- mauvaise borne polygone & rectangle

Un bon exemple est 'examples/fancy.dot'
