Indent
Add inverse NODE->index lookup table
Add simple s-t DFS heuristic for Random pricer #4

Implement 'greedy' DFS. Visit furthest adjacent nodes
first (arcs with greater weight).
If the weight of the path is greater than 'w', then we found
an improving column with reduced cost > 0.

Also, replace st.first/st.second with s/t.
Merge branch 'master' of github.com:sbebo/MMF