DNS Zones: List / Get (#271)

* Add Zone List / Get Support

* Addressing code review comments

* Adding v2 to DNS client

* List / Get unit tests plus updates to results for unit tests to work.

* DNS v2 List acceptance tests

* add failing unit test for dns v2 allpages

* Changing acceptance test for DNS v2 to use AllPages

* Adding empty zones.go file for package requirements

* Change ttl back to int

* DNS v2 Zones ListOpts
diff --git a/acceptance/clients/clients.go b/acceptance/clients/clients.go
index 8bf4aa3..aa57497 100644
--- a/acceptance/clients/clients.go
+++ b/acceptance/clients/clients.go
@@ -174,6 +174,25 @@
 	})
 }
 
+// NewDNSV2Client returns a *ServiceClient for making calls
+// to the OpenStack Compute v2 API. An error will be returned
+// if authentication or client creation was not possible.
+func NewDNSV2Client() (*gophercloud.ServiceClient, error) {
+	ao, err := openstack.AuthOptionsFromEnv()
+	if err != nil {
+		return nil, err
+	}
+
+	client, err := openstack.AuthenticatedClient(ao)
+	if err != nil {
+		return nil, err
+	}
+
+	return openstack.NewDNSV2(client, gophercloud.EndpointOpts{
+		Region: os.Getenv("OS_REGION_NAME"),
+	})
+}
+
 // NewIdentityV2Client returns a *ServiceClient for making calls
 // to the OpenStack Identity v2 API. An error will be returned
 // if authentication or client creation was not possible.