Setting and reporting the random seed for random graphs

[Islast]

To ensure reproducibility of BrainNetworksInPython analyses, we would like to be able to set and record the random seeds used to generate random graphs.
networkx doesn't currently support this, and in our regression tests we handle this by setting the global seed.
In the present dev branch of networkx they are introducing this functionalty link. It might be best to hold on until this release.

[Islast]

ME-ICA/tedana#87

[Islast]

networkx version later than 2.2 is now required for this reason