title: rollup, coffeescript issue when i dont use coffescript
body: <p>Trying to add rollup to my babel codebase. </p>
  
  <p>I'm getting an error related to coffee script when my code has no coffee script. I'm new to rollup so any help would be appreciated</p>
  
  <p>Seems to be a library called <code>config</code> but I have no idea what might be using that. </p>
  
  <pre><code>[!] Error: Could not resolve 'coffee-script' from /Users/terencechow/workspace/my-project/node_modules/config/lib/config.js
  Error: Could not resolve 'coffee-script' from /Users/terencechow/workspace/my-project/node_modules/config/lib/config.js
      at /Users/terencechow/workspace/my-project/node_modules/rollup-plugin-node-resolve/dist/rollup-plugin-node-resolve.cjs.js:85:23
      at /Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:50:13
      at processDirs (/Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:182:39)
      at ondir (/Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:197:13)
      at load (/Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:80:43)
      at onex (/Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:105:17)
      at /Users/terencechow/workspace/my-project/node_modules/resolve/lib/async.js:26:73
      at FSReqWrap.oncomplete (fs.js:112:15)
  </code></pre>
  
  <p>// rollup.config.js</p>
  
  <pre><code>import resolve from 'rollup-plugin-node-resolve'
  import babel from 'rollup-plugin-babel'
  import commonjs from 'rollup-plugin-commonjs'
  import json from 'rollup-plugin-json'
  import yaml from 'rollup-plugin-yaml'
  import coffee from 'rollup-plugin-coffee-script'
  
  export default {
    input: 'server/app.js',
    output: {
      file: 'dist/bundle.js',
      format: 'cjs'
    },
    plugins: [
      json(),
      yaml(),
      resolve({ extensions: [ '.js', '.json', .yaml', '.yml' ] }),
      commonjs({ extensions: [ '.js', '.json', '.yaml', '.yml' ] }),
      babel()
    ]
  }
  </code></pre>