Add ESP32 support

[DeeKey]

We need to add support for ESP32 based board flashing in order to support Sensor Kit 2.

[timmydan]

I had the same problem but got around it by finding and replacing both instances of "chip_id" (lines 496 and 642 in airrohr-flasher.py) with "read_mac" and then recompiling. This is new to me so I might not have understood all the complexities, but it seems that ESP32 doesn't use the command chip_id so read_mac is the closest thing. It ran fine after I made that change. I haven't yet connected it up to the other hardware, so consider this an answer-in-progress.

[pjgueno]

It is in the esptool.py. We should write a conditional statement or use this function:
def chip_id(esp, args): try: chipid = esp.chip_id() print('Chip ID: 0x%08x' % chipid) except NotSupportedError: print('Warning: %s has no Chip ID. Reading MAC instead.' % esp.CHIP_NAME) read_mac(esp, args)

[thepapermen]

I've createad a pull request with this fix, hopefully someone can test it on both ESP32 and ESP8266.

#68