title: eslint/eslint-plugin-react:not finding .jsx files
body: <p>I'm using <code>eslint</code> on a react app for the first time, and while it's checking .js files perfectly well, it's not finding any .jsx files. Admittedly my understanding is hazy, but I thought <code>eslint-plugin-react</code> automatically scanned .jsx files as well with <code>parserOptions.ecmaFeatures.jsx</code> set to true?</p>
  
  <p>If I run <code>npm run:lint -- --ext .jsx</code> then jsx files are scanned correctly, but not with a default <code>npm run:lint</code> command</p>
  
  <p>My .eslintrc here:</p>
  
  <pre><code>{
    "plugins": [
      "react"
    ],
    "parserOptions": {
      "ecmaVersion": 6,
      "sourceType": "module",
      "ecmaFeatures": {
        "jsx": true
      }
    },
    "env": {
      "es6":     true,
      "browser": true,
      "node":    true,
      "mocha":   true,
      "jest": true
    },
    "extends": [
      "eslint:recommended",
    "plugin:react/recommended"
    ],
    "rules": {
    }
  }
  </code></pre>