update included libusb to 1.0.17

must disable udev for now, because we don't ship udev and it is
enabled by default
specify libusbx for homebrew

libusb installs libusb 1.0.9, which is way out of date and doesn't pass tests.
Merge pull request #12 from colindean/update-libusb-1.0.17

update to libusbx 1.0.17 and fix homebrew install instructions