Update docs post-pytest overhaul

[willkg]

r?

[willkg]

This updates all the documentation with py.test things plus adds a pytest.ini file which I think reduces some of the command-line stuff you have to do to run the tests.

@paulcollinsiii Can you review this and point out issues?

[willkg]

^^^ I amended to the commit.

@paulcollinsiii Any other thoughts?

[paulcollinsiii]

naw man, looks good to me =)

[willkg]

Awesome! Thank you for looking at it!