Correct return value for scan function.
Add Sphinx documentation.
Ignore build files in documentation.
Guard with if __name__ == "__main__".
Use command-line argument to determine persistence
Add hardware instructions to README.
Update README with test instructions.
Update docstrings.
Remove old test files.
Remove old Sphinx files.
Update Sphinx table of contents.
Update global threshold for display.
Add instruction for how to clear persistence.
Do not except error if USB not connected.
More instructions in README.