finishes the current recording, passes the recorded sequence to the stored
callback, and sets Mousetrap.handleKey back to its original function

@returns void
function _finishRecording() {
        if (_recordedSequenceCallback) {
            _normalizeSequence(_recordedSequence);
            _recordedSequenceCallback(_recordedSequence);
        }

        // reset all recorded state
        _recordedSequence = [];
        _recordedSequenceCallback = null;
        _currentRecordedKeys = [];
    }