Add Zuul to airship-tempest-plugin

This patch set sets up Zuul checks/gating with a noop check. Until
some other in-flight PSs are merged no tox commands will run due to
import errors. Merging this to add Zuul to the project will allow
said PSs to get verified +1, and merged. Afterwards the templates
section in .zuul.yaml can be uncommented to add running py27/py35
unit tests with tox, as well as pep8.

Change-Id: I8c448c31d6e5b2ca870fa1d2c24c90b68c78a8c6

.zuul.yaml

@@ -0,0 +1,22 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+- project:
+#    templates:
+#      - openstack-python-jobs
+#      - openstack-python35-jobs
+    check:
+      jobs:
+        - noop
+    gate:
+      jobs:
+        - noop