update for library manager

Updated the README for version 1.1.1.

Put our standard note at the top of each source file.

- Fixed it to work properly with multiple instances.

- Improved the debouncing logic and reduced the width of PrevTimeMillis
variables.

These files were copied from pololu/zumo-shield@8c4e8f5.

Initial commit. These files were copied from pololu/zumo-shield@a02cf00.