Add basic server status page at /status.

Lists versions of various dependencies plus some Postgres and Redis
metrics.

test/functional/status_controller_test.rb

@@ -0,0 +1,20 @@
+require 'test_helper'
+
+class StatusControllerTest < ActionDispatch::IntegrationTest
+  context "The status controller" do
+    should "work for a html response" do
+      get status_path
+      assert_response :success
+    end
+
+    should "work for a json response" do
+      get status_path(format: :json)
+      assert_response :success
+    end
+
+    should "work for an xml response" do
+      get status_path(format: :json)
+      assert_response :success
+    end
+  end
+end