Allow single name component repository names

Private registries should support having images pushed with only a single name component (e.g. localhost:5000/myapp).
The public registry currently requires two name components, but this is already enforced in the registry code.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

docs/v2/routes_test.go

@@ -51,6 +51,14 @@ func TestRouter(t *testing.T) {
 			RequestURI: "/v2/",
 			Vars:       map[string]string{},
 		},
+		{
+			RouteName:  RouteNameManifest,
+			RequestURI: "/v2/foo/manifests/bar",
+			Vars: map[string]string{
+				"name": "foo",
+				"tag":  "bar",
+			},
+		},
 		{
 			RouteName:  RouteNameManifest,
 			RequestURI: "/v2/foo/bar/manifests/tag",