[CC1101] Added missing listen mode command (#72)

examples/CC1101/CC1101_Receive_Interrupt/CC1101_Receive_Interrupt.ino

@@ -70,6 +70,7 @@ void setup() {
   // cc.sleep()
   // cc.transmit();
   // cc.receive();
+  // cc.readData();
 }
 
 // flag to indicate that a packet was received
@@ -142,6 +143,9 @@ void loop() {
 
     }
 
+    // put module back to listen mode
+    cc.startReceive();
+
     // we're ready to receive more packets,
     // enable interrupt service routine
     enableInterrupt = true;