Prop type warning when passing a non String value as a key

[bampisSyk]

Issue description

I've came across a proptype warning when passing an int as options key.
focusItem is declared as a string in App.js seems reasonable enough so i think a simple conversion is enough as a think many people may try to pass an int as the option key, my case was passing the product_id from a an api.

I know that this is against the PropTypes use but i think an exception here adds some kind of flexibility

Steps to reproduce the issue

Just pass an int as the options key, you can try it in the PlayGround.js file

What's the expected result?

I think a conversion, maybe wrong

What's the actual result?

A proptype warning

Additional details / screenshot

A fix maybe bampisSyk@9a987e6

[stratos-vetsos]

Very nice remark!

Is "focusedItem" the only prop related to options, that excepts a string? Or we should consider normalize all the options before we pass it down to the component?

A pull request will be really helpful!
Thanks a lot

[bampisSyk]

About to do some more digging... i'll post back the results

[stratos-vetsos]

Any feedback on this?