Removing second base64 encoding

As per AWS documentation (http://docs.aws.amazon.com/kinesis/latest/APIReference/API_PutRecord.html#API_PutRecord_RequestSyntax) : "The data blob to put into the record, which is base64-encoded when the blob is serialized. The maximum size of the data blob (the payload before base64-encoding) is 50 kilobytes (KB)". Encoding before we send the data blob produces doubly encoded data strings.