Update installation and testing instructions

[zakv]

Fixes #113.

This PR updates the suggested editable installation instructions to use pip install -e instead of python setup.py develop as the former is preferred. Similarly it updates the suggested command for testing to pytest from python setup.py test which is now deprecated.

[charmasaur]

Thanks Zak!

BTW if you have the powers to merge PRs like this without approval you should just go for it (and if you can't then let me know and I'll try to change the settings). If you want me to take a look at something in particular then feel free to add me as a reviewer, but otherwise I probably won't check for new PRs too often.

[zakv]

Sounds good! I do have the power to merge PRs, and often do so. Sometimes I leave them up a few days before merging in case you're interested in checking them out. I'm sure you're plenty busy with other stuff and you have no obligation to take a look at these; I just thought I'd give you the opportunity as a courtesy!

Given that it sounds like you don't plan on looking at most PRs, and they can always be rolled back if necessary, I'll likely merge things faster from now on. I still might wait a bit anyway though just so that I have a chance to look at them with fresh eyes before merging. Don't feel the need to look at them though, I'll be sure to request a review from you if I really think it's necessary

[charmasaur]

Makes sense, I appreciate the thoughtfulness! The context is that I'm finishing up at Q-CTRL, so will be less involved in this kind of thing day-to-day, but of course I'm still happy/keen to weigh in anywhere I might actually be useful.

[zakv]

Got it. I should be able to handle most things, but may ask for you high-level/conceptual input if I end up changing anything interesting with the NeuralNetLearner (though I don't have any plans to do that). Best of luck on your future endeavors!

[charmasaur]

Thanks Zak :)