Change Block Storage v1 Snapshots.CreatedAt Type (#31)

* Change Block Storage v1 Snapshots.CreatedAt Type

This commit changes the Snapshots.CreatedAt type from
gophercloud.JSONRFC3339Milli to gophercloud.JSONRFC3339MilliNoZ.

* Adding Description to expected results
diff --git a/openstack/blockstorage/v1/snapshots/testing/fixtures.go b/openstack/blockstorage/v1/snapshots/testing/fixtures.go
index 7bdc782..21be6f9 100644
--- a/openstack/blockstorage/v1/snapshots/testing/fixtures.go
+++ b/openstack/blockstorage/v1/snapshots/testing/fixtures.go
@@ -22,11 +22,21 @@
       "snapshots": [
         {
           "id": "289da7f8-6440-407c-9fb4-7db01ec49164",
-          "display_name": "snapshot-001"
+          "display_name": "snapshot-001",
+          "volume_id": "521752a6-acf6-4b2d-bc7a-119f9148cd8c",
+          "display_description": "Daily Backup",
+          "status": "available",
+          "size": 30,
+          "created_at": "2012-02-14T20:53:07"
         },
         {
           "id": "96c3bda7-c82a-4f50-be73-ca7621794835",
-          "display_name": "snapshot-002"
+          "display_name": "snapshot-002",
+          "volume_id": "76b8950a-8594-4e5b-8dce-0dfa9c696358",
+          "display_description": "Weekly Backup",
+          "status": "available",
+          "size": 25,
+          "created_at": "2012-02-14T20:53:08"
         }
       ]
     }
@@ -44,8 +54,13 @@
 		fmt.Fprintf(w, `
 {
     "snapshot": {
+        "id": "d32019d3-bc6e-4319-9c1d-6722fc136a22",
         "display_name": "snapshot-001",
-        "id": "d32019d3-bc6e-4319-9c1d-6722fc136a22"
+        "display_description": "Daily backup",
+        "volume_id": "521752a6-acf6-4b2d-bc7a-119f9148cd8c",
+        "status": "available",
+        "size": 30,
+        "created_at": "2012-02-29T03:50:07"
     }
 }
       `)
@@ -75,8 +90,13 @@
     "snapshot": {
         "volume_id": "1234",
         "display_name": "snapshot-001",
-        "id": "d32019d3-bc6e-4319-9c1d-6722fc136a22"
-    }
+        "id": "d32019d3-bc6e-4319-9c1d-6722fc136a22",
+        "display_description": "Daily backup",
+        "volume_id": "1234",
+        "status": "available",
+        "size": 30,
+        "created_at": "2012-02-29T03:50:07"
+  }
 }
     `)
 	})