Improve code clarity

[murkle]

Library works great, thanks for the pointer :)

The code would be clearer in constants.js if you did this instead of having placeholder 0x00 bytes that are later changed

eg

function getStartMeasurementCommand(channelMask) {
    return [
        0x18,
        0xff,
        0x01, (channelMask >> 0) & 0xff, (channelMask >> 8) & 0xff, (channelMask >> 16) & 0xff, (channelMask >> 24) & 0xff,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
    ];
}

const STOP_MEASUREMENTS = [0x19, 0xff, 0x00, 0xff, 0xff, 0xff, 0xff];

function getMeasurementPeriodCommand(measurementPeriodInMicroseconds) {
    // 32 + (161<<8) + (7<<16) + (0<<24) = 500,000 microseconds
    return [
        0x1b,
        0xff,
        0x00, (measurementPeriodInMicroseconds >> 0) & 0xff, // eg 32
        (measurementPeriodInMicroseconds >> 8) & 0xff, // eg 161
        (measurementPeriodInMicroseconds >> 16) & 0xff, // eg 7
        (measurementPeriodInMicroseconds >> 24) & 0xff, //eg 0
        0x00,
        0x00,
        0x00,
        0x00,
    ];
}