doc(README.md): document workaround for test state resetting

Author: arschles

_tests/README.md

@@ -0,0 +1,21 @@
+# Deis Integration Tests
+
+This directory contains [Ginkgo]/[Gomega] based integration tests, which exercise
+the Deis CLI to extensively test the platform.
+
+# Resetting Cluster State
+
+Periodically, tests may not clean up after themselves. While this is an ongoing issue,
+for which we're working on a permanent fix (possible in [this GH issue](https://github.com/deis/workflow/issues/125))),
+below are commands you can run to work around the failure:
+
+```console
+$ kubectl exec -it deis-workflow-qoxhz -- sh
+/app # ./manage.py shell
+Python 2.7.10 (default, Aug 13 2015, 12:27:27)
+[GCC 4.9.2] on linux2
+>>> from django.contrib.auth import get_user_model
+>>> m = get_user_model()
+>>> m.objects.exclude(username='AnonymousUser').delete()
+>>> m.objects.all()                                     
+```