Implement Tri-Connected Compoenets

[ergawy]

Implement dividing a graph into its tri-connected components as suggested by [0] or [1].

[0] Hopcroft, John E., and Robert Endre Tarjan. "Dividing a graph into triconnected components." SIAM Journal on Computing 2.3 (1973): 135-158.
[1] Gutwenger, Carsten, and Petra Mutzel. "A linear time implementation of SPQR-trees." International Symposium on Graph Drawing. Springer Berlin Heidelberg, 2000.