blink1-tool: note needing to escape hex color codes w/'#'

[todbot]

On some shells (bash on Raspbian confirmed), the '#' character is treated as a comment and so short-circuits blink1-tool argument parsing. Thus, this fails:

$ ./blink1-tool  --rgb #0000ff
./blink1-tool: option '--rgb' requires an argument

but these work:

./blink1-tool --rgb '#0000ff'
./blink1-tool --rgb 0000ff

Need to fix: blink1-tool usage page, blink1-tool page on blink1.thingm.com

h/t @jedgarpark