use struct for toggle endpoint

client.go

@@ -75,9 +75,7 @@ func (s *Client) SetState(selector string, state *State) ([]Result, error) {
 }
 
 func (s *Client) Toggle(selector string, duration float64) ([]Result, error) {
-	m := make(map[string]interface{})
-	m["duration"] = duration
-	j, err := json.Marshal(m)
+	j, err := json.Marshal(&Toggle{Duration: duration})
 	if err != nil {
 		return nil, err
 	}