RootController: Use an index method instead of get

The index method authorizes HEAD request, which are handy for load
balancers.

Change-Id: Iab12c89641ffd725c3fb8a6e097020a696f84a97

cloudkitty/api/root.py

@@ -117,7 +117,7 @@ class RootController(rest.RestController):
     v1 = v1_api.V1Controller()
 
     @wsme_pecan.wsexpose([APIVersion])
-    def get(self):
+    def index(self):
         """Return the version list
 
         """

cloudkitty/tests/gabbi/gabbits/root.yaml

@@ -0,0 +1,12 @@
+fixtures:
+  - ConfigFixture
+
+tests:
+  - name: test if / is publicly available
+    url: /
+    status: 200
+
+  - name: test if HEAD / is available
+    url: /
+    status: 200
+    method: HEAD