Use networkx.testing functions for testing bipartite projections

I think that this fixes the problems with bipartite projection tests in python 3.4 reported in #975. But I cannot test it at the moment. At my system (linux 64bit) it works with 2.7 and 3.3 (using `PYTHONHASHSEED=4` as @Arfrever reported).  

In this tests all nodes and edges are sortable, and by using `assert_nodes_equal ` and  `assert_edges_equal` from `networkx.testing` I think that we correctly deal with the hash randomization issue.