change all time fields to have type time.Time (#190)

* add Volume.Unmarshal

* add volumetenants.VolumeExt.Unmarshal

* create servers.Server time.Time fields

* json.Unmarshal can correctly handle time.RFC3339 (Server time fields)

* add v3 Token UnmarshalJSON method

* check for empty string when unmarshaling time

* add Member UnmarshalJSON

* v3 tokens.Token ExtractInto

* v3 trust.Trust UnmarshalJSON

* time.Time fields swift response objects

* time.Time fields for orchestration response objects

* time.Time fields for shared file systems response objects

* if we don't use pointers for the custom time fields, we don't need to check if they're nil

* style guide fixes: 'r' for receiver, 's' for struct

* remove unnecessary pointers from UnmarshalJSON methods
diff --git a/openstack/orchestration/v1/stackresources/testing/fixtures.go b/openstack/orchestration/v1/stackresources/testing/fixtures.go
index adcd4c6..e890337 100644
--- a/openstack/orchestration/v1/stackresources/testing/fixtures.go
+++ b/openstack/orchestration/v1/stackresources/testing/fixtures.go
@@ -28,8 +28,8 @@
 		},
 		LogicalID:    "hello_world",
 		StatusReason: "state changed",
-		UpdatedTime:  gophercloud.JSONRFC3339NoZ(time.Date(2015, 2, 5, 21, 33, 11, 0, time.UTC)),
-		CreationTime: gophercloud.JSONRFC3339NoZ(time.Date(2015, 2, 5, 21, 33, 10, 0, time.UTC)),
+		UpdatedTime:  time.Date(2015, 2, 5, 21, 33, 11, 0, time.UTC),
+		CreationTime: time.Date(2015, 2, 5, 21, 33, 10, 0, time.UTC),
 		RequiredBy:   []interface{}{},
 		Status:       "CREATE_IN_PROGRESS",
 		PhysicalID:   "49181cd6-169a-4130-9455-31185bbfc5bf",
@@ -99,8 +99,8 @@
 		},
 		LogicalID:    "hello_world",
 		StatusReason: "state changed",
-		UpdatedTime:  gophercloud.JSONRFC3339NoZ(time.Date(2015, 2, 5, 21, 33, 11, 0, time.UTC)),
-		CreationTime: gophercloud.JSONRFC3339NoZ(time.Date(2015, 2, 5, 21, 33, 10, 0, time.UTC)),
+		UpdatedTime:  time.Date(2015, 2, 5, 21, 33, 11, 0, time.UTC),
+		CreationTime: time.Date(2015, 2, 5, 21, 33, 10, 0, time.UTC),
 		RequiredBy:   []interface{}{},
 		Status:       "CREATE_IN_PROGRESS",
 		PhysicalID:   "49181cd6-169a-4130-9455-31185bbfc5bf",
@@ -177,7 +177,7 @@
 	LogicalID:    "wordpress_instance",
 	Attributes:   map[string]interface{}{"SXSW": "atx"},
 	StatusReason: "state changed",
-	UpdatedTime:  gophercloud.JSONRFC3339NoZ(time.Date(2014, 12, 10, 18, 34, 35, 0, time.UTC)),
+	UpdatedTime:  time.Date(2014, 12, 10, 18, 34, 35, 0, time.UTC),
 	RequiredBy:   []interface{}{},
 	Status:       "CREATE_COMPLETE",
 	PhysicalID:   "00e3a2fe-c65d-403c-9483-4db9930dd194",