Fix travis failure: more specific serial write capture comparison
Fix travis failure: more specific serial write capture comparison

See: https://travis-ci.org/rwaldron/johnny-five/builds/11160478
Signed-off-by: Rick Waldron <dd8fdbe95c7f81f312b273ef8860922803e9ef16@gmail.com>

cumbreras/rv,garrows/johnny-five,AnnaGerber/johnny-five,joelunmsm2003/arduino,kod3r/johnny-five,kod3r/johnny-five