Fix JSONP formatter, fixes T300

Summary:
By separating options fetching from the rest of the method, it becomes possible
to change them in extensions.

Test Plan:
```
bin/behat -c application/tests/behat.yml -f progress application/tests/features/api.posts.feature
```

Reviewers: eyedol, rjmackay

Reviewed By: eyedol, rjmackay

Subscribers: dkobia

Maniphest Tasks: T300

Differential Revision: https://phabricator.ushahidi.com/D124