Assure host is always an IP address (#69)

Use `InetAddress.getHostAddress()` instead of `InetAddress.getHostName()` to get the host IP. The second one sometimes returns a textual name of the local host and this info is not really useful as a source address unless there's a way to resolve that name.

android/src/main/java/com/tradle/react/UdpReceiverTask.java

@@ -47,7 +47,7 @@ protected Void doInBackground(Pair<DatagramSocket, UdpReceiverTask.OnDataReceive
                 final InetAddress address = packet.getAddress();
                 final String base64Data = Base64.encodeToString(packet.getData(), packet.getOffset(),
                     packet.getLength(), Base64.NO_WRAP);
-                receiverListener.didReceiveData(base64Data, address.getHostName(), packet.getPort());
+                receiverListener.didReceiveData(base64Data, address.getHostAddress(), packet.getPort());
             } catch (IOException ioe) {
                 if (receiverListener != null) {
                     receiverListener.didReceiveError(ioe.getMessage());