Oj was removed from sensu in version 0.13.0.

This swaps out the Oj parser for the JSON parser.

Here is a link to relevant section for the sensu changelog: [CHANGELOG.md](https://github.com/sensu/sensu/blob/c81c50a54bb746cfc6be952e75ed5ffcda2ccfb1/CHANGELOG.md#other-1)