Support encrypted transport, properly handle multiple recipients.

1) Add encryption support for the transport layer.  This obscures
   metadata from the push messaging provider.

2) Better support the direction multiple destination messages is
   headed (one unique message per recipient).

library/src/org/whispersystems/textsecure/push/PushTransportDetails.java

@@ -34,11 +34,11 @@ public class PushTransportDetails implements TransportDetails {
 
   @Override
   public byte[] getEncodedMessage(byte[] messageWithMac) {
-    return Base64.encodeBytesWithoutPadding(messageWithMac).getBytes();
+    return messageWithMac;
   }
 
   @Override
   public byte[] getDecodedMessage(byte[] encodedMessageBytes) throws IOException {
-    return Base64.decodeWithoutPadding(new String(encodedMessageBytes));
+    return encodedMessageBytes;
   }
 }