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/sharedfilesystems/v2/securityservices/results.go b/openstack/sharedfilesystems/v2/securityservices/results.go
index 746b2b3..6874208 100644
--- a/openstack/sharedfilesystems/v2/securityservices/results.go
+++ b/openstack/sharedfilesystems/v2/securityservices/results.go
@@ -1,6 +1,11 @@
 package securityservices
 
-import "github.com/gophercloud/gophercloud"
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/gophercloud/gophercloud"
+)
 
 // SecurityService contains all the information associated with an OpenStack
 // SecurityService.
@@ -28,9 +33,28 @@
 	// The security service host name or IP address
 	Server string `json:"server"`
 	// The date and time stamp when the security service was created
-	CreatedAt gophercloud.JSONRFC3339MilliNoZ `json:"created_at"`
+	CreatedAt time.Time `json:"-"`
 	// The date and time stamp when the security service was updated
-	UpdatedAt gophercloud.JSONRFC3339MilliNoZ `json:"updated_at"`
+	UpdatedAt time.Time `json:"-"`
+}
+
+func (r *SecurityService) UnmarshalJSON(b []byte) error {
+	type tmp SecurityService
+	var s struct {
+		tmp
+		CreatedAt gophercloud.JSONRFC3339MilliNoZ `json:"created_at"`
+		UpdatedAt gophercloud.JSONRFC3339MilliNoZ `json:"updated_at"`
+	}
+	err := json.Unmarshal(b, &s)
+	if err != nil {
+		return err
+	}
+	*r = SecurityService(s.tmp)
+
+	r.CreatedAt = time.Time(s.CreatedAt)
+	r.UpdatedAt = time.Time(s.UpdatedAt)
+
+	return nil
 }
 
 type commonResult struct {