Allow users to specify the yield time if they want to speed up loop processing.

Author: jburhenn

src/CayenneArduinoMQTTClient.h

@@ -83,9 +83,15 @@ class CayenneArduinoMQTTClient
 
 	/**
 	* Main Cayenne loop
+	*
+	* @param yieldTime  Time in milliseconds to yield to allow processing of incoming MQTT messages and keep alive packets.
+	* NOTE: Decreasing the yieldTime while calling write functions (e.g. virtualWrite) in your main loop could cause a 
+	* large number of messages to be sent to the Cayenne server. Use caution when adjusting this because sending too many 
+	* messages could cause your IP to be rate limited or even blocked. If you would like to reduce the yieldTime to cause your 
+	* main loop to run faster, make sure you use a timer for your write functions to prevent them from running too often. 
 	*/
-	void loop() {
-		CayenneMQTTYield(&_mqttClient, 1000);
+	void loop(int yieldTime = 1000) {
+		CayenneMQTTYield(&_mqttClient, yieldTime);
 		pollChannels(virtualChannels);
 #ifdef DIGITAL_AND_ANALOG_SUPPORT
 		pollChannels(digitalChannels);