Explicitly import graph atlas
Change bellman_ford to use the FIFO variant

The predecessor heuristic is also included.
Return empty graph for random 0-regular graph

There is exactly one 0-regular graph, namely the empty graph. A call to
`random_regular_graph(0, n)` now returns the empty graph on n nodes instead of
the null graph.
Adds test.
Merge pull request #1093 from jfinkels/patch-2

Return empty graph for random 0-regular graph
Add shortest augmenting path maxflow algorithm
Merge pull request #1091 from ysitu/bellman_ford

Change bellman_ford to use the FIFO variant
Merge pull request #1088 from hagberg/graph-atlas-import

Explicitly import graph atlas
Add two-phase option to shortest augmenting path maxflow algorithm
Fix phase 1 starting condition in shortest augmenting path maxflow
Add test for two-phase shortest augmenting path maxflow algorithm
symlink to copy of atlas.py example
Merge pull request #1098 from hagberg/graph-atlas-import

symlink to copy of atlas.py example
Doc fixes (bad module paths)
Merge pull request #1100 from hagberg/doc-fixes

Doc fixes (bad module paths)
Move auxiliary stuff used by maxflow algorithms to separate file
Modify handling of module conflict in shortest augmenting path maxflow
Merge pull request #1099 from ysitu/sap

Add shortest augmenting path maximum flow algorithm