How to update a plugin ?
You can upgrade an plugin (Visual Composer or other required plugins )by performing following steps:
1. Please make sure main theme is activated while performing other steps
2. Go to Plugins page in your WordPress Dashboard, locate Visual Composer ( for example ) in the list, deactivate it and delete it
3. You will see message that required plugin is missing at the top of your WordPress Dashboard
4. Install the plugin and then activate it
Or you can do this manually just copy the js_composer from pitch.zip and paste it into wp-content/plugins/