web: Add transfer fallback for PyPy
hidtrigger: Replace cython-hidapi with hidapi-cffi for PyPy compatibility
web: Replace spin.js with pure CSS activity indicator
Make huey.consumer less verbose in debug mode
hidtrigger: Fix typo
web: Refactor pypy-specific code
Update tests
Update documentation
Update version to 0.5dev
web: Return None when no external storage was found