Please throw an error for invalid events

[OmgImAlexis]

Currently if you pass an invalid/unused string to lock.on it just fails silently; because of this I spent the whole day trying to workout what was wrong only to finally realise that I had a typo in the string I was passing.

This should throw an error instead of doing nothing.

this.lock.on('INVAID_STRING', (error) => {
});