Incorrect accepting states for arbitrary topological ordering

[ChieloNewctle]

A topological ordering of states is not necessarily an ordering from link parents to their children.

The current implementation is correct, because the topological sorting is in a manner of BFS, where NO states with longer maximum suffix lengths are visited earlier than states with shorter ones.

So the interface name of get_topo_sorted_node_ids will soon be changed into a more precise one. And there will be another test to verify this property.

[ChieloNewctle]

#14