The I2C address is #defined [here](https://github.com/adafruit/Adafruit_GPS/blob/710c724dd2348afdcdc288ed0ef8966739094dc8/src/Adafruit_GPS.h#L46). But the address is used as a magic number [here](https://github.com/adafruit/Adafruit_GPS/blob/710c724dd2348afdcdc288ed0ef8966739094dc8/src/Adafruit_GPS.cpp#L305) Doesn't matter, but noticed while browsing for inspiration.
