update to ArmDev 2.0 and Setuptools

Move to the new way. Testing and development is way easier under ArmDev 2.0. Setuptools reduces boilerplate and is required anyway. All the Armstrong components will need a similar update (we recently made this change to armstrong/armstrong.core.arm_layout#19).

There's a new changelog and I rewrote the Readme. Setup.py now acknowledges that this is stable software. I dropped the ridiculous stuff from the dev requirements file and axed the unused base req file.