command line version

[Jonathan]

I managed to modify your code to allow it to be used from a script (i copied the same syntax as used by esptool.py)
if you want my changes let me know and i will fork your repo and do a pull request

main reason i did it was i found the esptool.py has an issue in it's stub code which messes up the EEPROM library read write code (seems to zero out the storage space on each boot) the same image file burnt with your code does not have these issues.