Compatiblity with oncoming pull requests from forks

[frextrite]

Does this not work with pull requests from forks? I'm getting the following error:

{
  "message": "Resource not accessible by integration",
  "documentation_url": "https://developer.github.com/v3/issues/labels/#add-labels-to-an-issue"
}
{
  "message": "Resource not accessible by integration",
  "documentation_url": "https://developer.github.com/v3/issues/labels/#remove-a-label-from-an-issue"
}

[smay1613]

👍 Please, add possibility to use labeler as scheduled job