Airflow-priority

What's Changed
* Only enable plugins if configuration options present by timkpaine in https://github.com/airflow-laminar/airflow-priority/pull/3
* Add discord and symphony alerts by timkpaine in https://github.com/airflow-laminar/airflow-priority/pull/4


**Full Changelog**: https://github.com/airflow-laminar/airflow-priority/compare/v0.1.0...v0.1.1

What's Changed
* initialize with aws, datadog, newrelic, and slack plugins by timkpaine in https://github.com/airflow-laminar/airflow-priority/pull/1

**Full Changelog**: https://github.com/airflow-laminar/airflow-priority/commits/v0.1.0