Release 0.2

I've added support for USB input, although that doesn't work reliably. Whenever the inverter is shutdown, the USB port won't recognise commands after that. So every morning it will have stoped working. This problem seems due to the inverter more than to the script.

A hardware workaround could be to place some sort of automated switch between the USB and the inverter that switches with a delay time to allow the inverter to start, but I haven't got around to trying that.

Hobby release

This version should work.