Fix mesh.begin() (#214)

* Fix mesh.begin()

- Begin will return true by mistake because of recent changes to the renewAddress() function

* Oops

RF24Mesh.cpp

@@ -35,7 +35,7 @@ bool RF24Mesh::begin(uint8_t channel, rf24_datarate_e data_rate, uint32_t timeou
     network.returnSysMsgs = true;
 
     if (getNodeID() > 0) { //Not master node
-        if (!renewAddress(timeout)) {
+        if (renewAddress(timeout) == MESH_DEFAULT_ADDRESS) {
             return false;
         }
     }