dillon1000/react

Update refs-and-the-dom.md (#8250)

Since a lot of projects use [airbnb eslint config](https://www.npmjs.com/package/eslint-config-airbnb) where [this rule](http://eslint.org/docs/rules/no-return-assign) is enabled (and its a good rule) some people might get confused when they are trying this out in their project.