DefaultHttpProvider body encoding problem #95

Expected behavior

in DefaultHttpProvider#sendRequestInternal line 257

logger.logDebug("Sending " + serializable.getClass().getName() + " as request body");
final String serializeObject = serializer.serializeObject(serializable);
bytesToWrite = serializeObject.getBytes();

change body String to byte using String#getBytes it depends on platform's default charset

I use utf-8 and it may not work properly depending on the platform environment.

It would be better if could set up in DefaultClientConfig.