Currently uploading via the Arduino IDE and PlatformIO works. But it's not perfect yet:
1. We're using a custom-compiled bootloader for the e73 board, which is nice;
2. We're still using `board = adafruit_feather_nrf52832` in the `platformio.ini` file. Using our custom board `boards/e73-tbb.json` doesn't work yet. Uploading results in a `*** [upload] IndexError : list index out of range` error. Most likely has to be fixed in https://github.com/platformio/platform-nordicnrf52/blob/develop/builder/main.py.
