Add an option for continuous recording.

[AndriySvyryd]

Currently Mousetrap.record will only record one sequence. For my scenario it would be useful to keep recording the key sequences until canceled ( Mousetrap.stopRecord)

A naïve workaround of starting recording again in the callback doesn't work as the state is cleared after the callback is called:

recordKey() {
    Mousetrap.record(keys => {
        console.log(keys.join(' '));
        this.recordKey();
    });
}