TM1638 or TM1640 LED Keypad driver.
Notes:
- Imported into GitHub here from https://code.google.com/p/tm1638-library/
- Current source code repo is located at: https://github.com/rjbatista/tm1638-library
- this repo shall be archived and replaced by a fork of https://github.com/rjbatista/tm1638-library with my corrections