Added SMS transport support for PreKeyBundle messages.

1) Added SMS transport support.

2) Keep track of whether a PreKeyBundle message has gotten
   a response, and send them as subsequent messages until
   one has been received.

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

@@ -0,0 +1,44 @@
+/**
+ * Copyright (C) 2013 Open Whisper Systems
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.whispersystems.textsecure.push;
+
+import org.whispersystems.textsecure.crypto.TransportDetails;
+import org.whispersystems.textsecure.util.Base64;
+
+import java.io.IOException;
+
+public class PushTransportDetails implements TransportDetails {
+  @Override
+  public byte[] getStrippedPaddingMessageBody(byte[] messageWithPadding) {
+    return messageWithPadding;
+  }
+
+  @Override
+  public byte[] getPaddedMessageBody(byte[] messageBody) {
+    return messageBody;
+  }
+
+  @Override
+  public byte[] getEncodedMessage(byte[] messageWithMac) {
+    return Base64.encodeBytesWithoutPadding(messageWithMac).getBytes();
+  }
+
+  @Override
+  public byte[] getDecodedMessage(byte[] encodedMessageBytes) throws IOException {
+    return Base64.decodeWithoutPadding(new String(encodedMessageBytes));
+  }
+}