* Add isort to pre-commit

* Run isort on all python files (except __init__.py ones)

find networkx -name \*.py -exec pyupgrade --py36-plus {} \;

The copyright and author stuff is not necessary, out-of-date,
and inconsistent.  It takes up visual space and is a pain to
police everyone doing the same thing on the top of the module.

Git handles authorship in a comprehensive and authoritative way.
The LICENSE.txt file applies to all project code.

Fixes #3258

* Fixed problem in documentation view of this function

* Replacing `Return` to `Returns` in function docs

Fixes #1764 

* Add a doc page to explain random number generator handling

* replace deprecated numpy.random.random_integers with randint

* First set of random_state decorator updates... utils and some generators

* protect numpy import from failure is not there

* fix doctests in randomness.rst

* Update algorithms for new random_state paradigm

* Fix tests dependent on python version

* Update random_state paradigm in rest of the modules

* fix tests for wierd cases.

windows 32bit doesn't like big seeds.
smallworld wasn't sending seed to utils.discrete_sequence

* Add tests.  Rewrite randomstate interface class to fix tests

* anogther tweak for osx with no deps

* improve doc examples for seed. Check all functions for seed independence.

Calling with int seed should not affect global RNG

* Add testing script and add more variates to RandomInterface

* fix typo and remove unneeded file causing nodetest trouble

* fix doctest for randomness.rst