Dropbox plugin secretkey error

I tried creating a json with the secret key and also by setting the environment variable but still ended up getting this error

```
Dropbox config found in environment. Plugin enabled. (Key: "----")
/home/curator-analyst-04/Documents/apps/dillinger/plugins/dropbox/dropbox.js:41
  dbx.setClientSecret(dropbox_config.app_secret);
      ^

TypeError: dbx.setClientSecret is not a function
```
