Change naming scheme for API requests

This change uses 'enqueued_at' and 'worker_type' instead of 'enqueuedAt' and 'workerType'. This reflects the changes made in https://github.com/michaelmarconi/oncue/commit/9c8132415fa036d8c3a97802ce69560c3d5e0f23.

The wiki in oncue has been updated. See https://github.com/michaelmarconi/oncue/wiki/RESTful-API.