title: ESLint React PropTypes, 'prop' is missing in prop validation
body: <p>I have a stateless react component</p>
  
  <pre><code>import React from 'react'
  import styled from 'styled-components';
  import PropTypes from 'prop-types';
  
  export default props =&gt; &lt;StyledButton&gt;{props.children}&lt;/StyledButton&gt;
  
  StyledButton.propTypes = {
      children: PropTypes.node,
  }
  StyledButton.defaultProps = {
      children: null,
  }
  </code></pre>
  
  <p>And a class component</p>
  
  <pre><code>class Thumbnail extends React.Component {
      constructor(props) {
          super(props)
          this.state = {
             color: 'red',
          }
      }
      render() {
          return (
             &lt;button&gt;{this.props.children}&lt;/button&gt;
         )
      }
  }
  
  Thumbnail.propTypes = {
      children: PropTypes.node,
  }
  Thumbnail.defaultProps = {
      children: null,
  }
  </code></pre>
  
  <p>My eslintrc file</p>
  
  <pre><code>module.exports = {
  "extends": "airbnb",
  "plugins": [
      "react",
      "jsx-a11y",
      "import"
  ],
  "rules": {
      "react/jsx-filename-extension": 0,
      "semi": 0,
      "indent": ["error", 4],
      "react/jsx-indent": 0,
      "jsx-a11y/img-redundant-alt": 0
  }
  };
  </code></pre>
  
  <p>Eslint complains that 'children is missing in prop validation' in the stateless component.
  But it's fine in the class component.</p>
  
  <p>Spent 2 hours trying to fix this, Any help would be greatly appreciated</p>