Adds os-server-groups

This commit adds support for the os-server-groups extension. This allows
users to create scheduling policies for launching instances.
diff --git a/openstack/compute/v2/extensions/servergroups/requests_test.go b/openstack/compute/v2/extensions/servergroups/requests_test.go
new file mode 100644
index 0000000..07fec51
--- /dev/null
+++ b/openstack/compute/v2/extensions/servergroups/requests_test.go
@@ -0,0 +1,59 @@
+package servergroups
+
+import (
+	"testing"
+
+	"github.com/rackspace/gophercloud/pagination"
+	th "github.com/rackspace/gophercloud/testhelper"
+	"github.com/rackspace/gophercloud/testhelper/client"
+)
+
+func TestList(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+	HandleListSuccessfully(t)
+
+	count := 0
+	err := List(client.ServiceClient()).EachPage(func(page pagination.Page) (bool, error) {
+		count++
+		actual, err := ExtractServerGroups(page)
+		th.AssertNoErr(t, err)
+		th.CheckDeepEquals(t, ExpectedServerGroupSlice, actual)
+
+		return true, nil
+	})
+	th.AssertNoErr(t, err)
+	th.CheckEquals(t, 1, count)
+}
+
+func TestCreate(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+	HandleCreateSuccessfully(t)
+
+	actual, err := Create(client.ServiceClient(), CreateOpts{
+		Name:     "test",
+		Policies: []string{"anti-affinity"},
+	}).Extract()
+	th.AssertNoErr(t, err)
+	th.CheckDeepEquals(t, &CreatedServerGroup, actual)
+}
+
+func TestGet(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+	HandleGetSuccessfully(t)
+
+	actual, err := Get(client.ServiceClient(), "4d8c3732-a248-40ed-bebc-539a6ffd25c0").Extract()
+	th.AssertNoErr(t, err)
+	th.CheckDeepEquals(t, &FirstServerGroup, actual)
+}
+
+func TestDelete(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+	HandleDeleteSuccessfully(t)
+
+	err := Delete(client.ServiceClient(), "616fb98f-46ca-475e-917e-2563e5a8cd19").ExtractErr()
+	th.AssertNoErr(t, err)
+}