title: Error when starting watchman
body: <p>hi when i want to start my app with 'react-native start', i get this error. Somebody know what to do? I tried to change the permission of the watchman folder and the project folder to chmod -R 777 'path'</p>
  
  <pre><code>Metro Bundler ready.
  
  Loading dependency graph...watchman warning:  opendir(/home/t/react/testApp/android/app/build/generated/source/r/debug/com) -&gt; Permission denied. Marking this portion of the tree deleted
  Recrawled this watch 1 times, most recently because:
  /home/t/react/testApp: dir missing from internal state
  To resolve, please review the information on
  https://facebook.github.io/watchman/docs/troubleshooting.html#recrawl
  To clear this warning, run:
  `watchman watch-del /home/t/react/testApp ; watchman watch-project /home/t/react/testApp`
  
  opendir(/home/t/react/testApp/android/app/build/generated/source/r/debug/com) -&gt; Permission denied. Marking this portion of the tree deleted
  Recrawled this watch 1 times, most recently because:
  /home/t/react/testApp: dir missing from internal state
  To resolve, please review the information on
  https://facebook.github.io/watchman/docs/troubleshooting.html#recrawl
  To clear this warning, run:
  `watchman watch-del /home/t/react/testApp ; watchman watch-project /home/t/react/testApp`
  
  Loading dependency graph, done.
  </code></pre>