Initial basic, minimal setup.py.
Currently relies on usb and this is not declared in requirements.
Version tuple  is stored in names that matches Python sys module.
Allow setup.py to run if pyusb is missing.
Start of adding requirements.
Added pyusb requirements.
Refactor required pyusb version, only set version in one place.
Reduce minimum pyusb version (unless on windows)
Merge pull request #11 from clach04/add_setup_py

Initial basic, minimal setup.py.