Benchmark tests on a random digraph (n = 100000, m = 1000000)

ListDigraph - Building                  0.316598
ListDigraph (sorted arcs) - Building    0.233748
SmartDigraph - Building                 0.122141
SmartDigraph (sorted arcs) - Building   0.106241

ListDigraph - Iteration
  NodeIt:    0.000802398    	0.000793099
  ArcIt:     0.086284    	0.0865654
  OutArcIt:  0.0818583
  InArcIt:   0.0817522

ListDigraph (sorted arcs) - Iteration
  NodeIt:    0.000796008    	0.000793099
  ArcIt:     0.0821322    	0.0824809
  OutArcIt:  0.0117641
  InArcIt:   0.07757

SmartDigraph - Iteration
  NodeIt:    9.07898e-05    	9.12189e-05
  ArcIt:     0.000905609    	0.000905609
  OutArcIt:  0.0796772
  InArcIt:   0.0795413

SmartDigraph (sorted arcs) - Iteration
  NodeIt:    9.13858e-05    	9.05991e-05
  ArcIt:     0.0009058    	0.000905585
  OutArcIt:  0.0085053
  InArcIt:   0.0750944