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I am following a React tutorial here. In the fourth lesson it has me create a App.propTypes section. When I run the code React gives me a error saying TypeError: Cannot read property 'string' of undefined when I open up my console the error says React.PropTypes is deprecated since React 15.5.0, use the npm module prop-types instead. I then went ahead and installed the npm package prop-types and imported it in my code, but I still end up with the same error. I will include my code below.

I am using node version v8.5.0. Maybe I should try and find out what version of node the tutorial is using so my React version matches up, but I don't even know if I can find that out, I wish tutorials would specify these sorts of things, it looks like this tutorial is 2 years old, which is probably why I am having this discrepancy.

src/app.js