add neopixel status; fix baud=0 issue; improve debug output

[tve]

This PR has a number of fixes / improvements. I don't really expect it to be mergeable as-is and would appreciate what is desirable and what isn't.

On my esp8266 board I added a neopixel to show the status of the link using colors. Pretty simple and useful, but obviously not everyone has or wants that. Code could be wrapped in a #define or could add a config param.

I added a fix for the issue mentioned at the end of #47, which is that if the baud rate ends up being set to 0 the sketch crashes.

I added additional debug output, added CR for the LF-terminated lines, and enabled the Espressif SDK debug output. I find that when things don't work the more info I get the better. It doesn't spew stuff during normal operation, so I don't think it has any effect on performance.