Fix tests for cuts.
Fix example for random_bipartite

The check of a connected graph doesn't play any role in the example.
Very rarely it gave an error to nosetests.
Add pypy test to travis-ci
Merge pull request #906 from dschult/cuttestfixes

Fix some tests and examples that sometimes failed
Add some extra packages in travis-ci test config
Merge branch 'master' of github.com:networkx/networkx
Adjust travis-ci config
Add more packages to travis-ci config
Adjust travis.ci config (Python3 config needed)
Turn on verbose testing to see what is skipped with travis.ci