* Implement flashing lights if battery level is too low (use fuelgauge.isAlerting() and setAlertThreshold())
  * Need to implement PIR distance sensor to verify door of safe closed
  * Need to add support for Adafruit Trinket Pro
  * Add note about adjusting values for distance
  * Finish Fritzing documentation (breadboard / schematic)
  * Bill of Materials for all pieces/parts/etc