Twitter app needs read and write permissions

[techieshark]

After following the deployment instructions, I can select a list and click the 'Follow all members of this list' button but then I get the following:

Running heroku logs results in this output, with the key line appearing to be:

Twitter::Error::Unauthorized (Read-only application cannot POST.):

Changing the permission to read+write seemed to fix that (after also updating the config vars with the new consumer key and secret).