title: require is not defined using rollup
body: <p>I have the following <code>rollup.config.js</code>:</p>
  
  <pre><code>import commonjs from 'rollup-plugin-commonjs';
  import nodeResolve from 'rollup-plugin-node-resolve';
  
  export default {
    input: 'input.js',
    output: {
      file: 'output.js',
      format: 'iife'
    },
    plugins: [
      nodeResolve(
        {
          jsnext: true,
          main: true
        }
      ),
      commonjs({ include: 'hello.js' })
    ]
  }
  </code></pre>
  
  <p>I have the following <code>input.js</code> which <code>require</code>s <code>hello.js</code>:</p>
  
  <pre><code>var hello = require('./hello.js');
  
  console.log(hello);
  </code></pre>
  
  <p>and <code>hello.js</code> is simply:</p>
  
  <pre><code>module.exports = 'hello';
  </code></pre>
  
  <p>I would like <code>output.js</code> to not include the <code>require</code> syntax and for it to be replaced it with the string <code>'hello'</code>.</p>
  
  <p>I instead still see the line <code>var hello = require('./hello.js');</code></p>
  
  <p>How can I replace this line with a rollup plugin? (I thought that is what the commonjs plugin was for).</p>
  
  <p>Thanks in advance for the help!</p>