Add more serial:// options

[wybiral]

The serial package being used supports multiple options beyond the baud rate which might be useful to expose as optional arguments.

We should add more options to the serial protocol. See comment below.

[wybiral]

That serial package is no longer being used in v2 because of #27

The one currently being used is this package.

Good options to provide would probably be:

• Data bits (maps to serial.Config.Size)
• Parity (maps to serial.Config.Parity)
• Stop bits (maps to serial.Config.StopBits)

The current defaults are for 8-N-1. It's probably a good idea to look at other tools that take in these options and see if there's an implied standard for supplying these.