Flush std::cout after each solution

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Implement simple "minimum length" forecast

This looks how much the current solution grows if all subsequent
transitions have the minimal cost.

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Expose Distance_matrix::min_cost() to python

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Add some debug output to the integration test

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>