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

ListDigraph - Building                  0.317591
ListDigraph (sorted arcs) - Building    0.234466
SmartDigraph - Building                 0.12351
SmartDigraph (sorted arcs) - Building   0.106032

ListDigraph - Iteration
  NodeIt:    0.000774407    	0.00076611
  ArcIt:     0.0863143    	0.0865564
  OutArcIt:  0.0817103
  InArcIt:   0.0817481

ListDigraph (sorted arcs) - Iteration
  NodeIt:    0.000776505    	0.000771689
  ArcIt:     0.0821834    	0.0824024
  OutArcIt:  0.0117822
  InArcIt:   0.0775104

SmartDigraph - Iteration
  NodeIt:    9.06944e-05    	9.07183e-05
  ArcIt:     0.000905395    	0.000905299
  OutArcIt:  0.079576
  InArcIt:   0.0794058

SmartDigraph (sorted arcs) - Iteration
  NodeIt:    9.0909e-05    	9.07183e-05
  ArcIt:     0.000905299    	0.000905299
  OutArcIt:  0.00849619
  InArcIt:   0.0750465