optimize OutputEventFilter for large stdout streams

update our event data search algorithm to be a bit lazier in event data
discovery; this drastically improves processing speeds for stdout >5MB

see: https://github.com/ansible/awx/issues/417

requirements/requirements_dev.txt

@@ -10,6 +10,7 @@ pytest-cov
 pytest-django
 pytest-pythonpath
 pytest-mock
+pytest-timeout
 logutils
 flower
 uwsgitop