GraphReader implementation ideas.
+ Question: Why we need common input interface?
1 hier: hierarchygraph.h hierarchygraph_test.cc
2 g++ -Wall -W -I../.. -I../klao -I../../lemon hierarchygraph_test.cc -o test
4 edge: edgepathgraph_test.cc edgepathgraph.h
5 g++ -Wall -W -I../.. -I../klao -I../../lemon edgepathgraph_test.cc -o test