Minimum Node Version? (10?)

[AlbinoDrought]

While playing locally with the event emitter, I noticed the method off didn't exist for me - I found out it was added in node 10 (and of course I'm running an outdated version, as always).

Would it make sense to require Node >= 10 in package.json? Not sure what conflicts this could cause, what version Travis CI is running, etc

[cocoastorm]

For Travis CI we can probably configure the right or even multiple node.js versions. Also, I think supporting the LTS version (which I think is v8 right now?) is probably better.

Does the off method have a shim or polyfill we can optionally add in?

Then again limiting to just Node >= 10 doesn't seem awful.

[AlbinoDrought]

I think removeEventListener does the same thing as off, but just looks more unwieldly.

(honestly not sure of differences between LTS and 10 - still have async/await support and all that jazz?)

[cocoastorm]

I was looking at your recent PR, looks like we use a couple of modern features of ECMAScript :)

• const and let
• async and await (like you said)
• object spread syntax
• object.entries

I'd like to think Node.js v8 has most of this. We'll see, restricting it to Node.js 10 for now shouldn't be that big of a deal...