@JsonProperty
    public long seed() {
        return seed;
    }
This class behaves identically to TimestampRandomPayloadGenerator, except the message size follows a gaussian
distribution.

This should be used in conjunction with TimestampRecordProcessor in the Consumer to measure true end-to-end latency
of a system.

`messageSizeAverage` - The average size in bytes of each message.
`messageSizeDeviation` - The standard deviation to use when calculating message size.
`messagesUntilSizeChange` - The number of messages to keep at the same size.
`seed` - Used to initialize Random() to remove some non-determinism.

Here is an example spec:

{
   "type": "gaussianTimestampRandom",
   "messageSizeAverage": 512,
   "messageSizeDeviation": 100,
   "messagesUntilSizeChange": 100
}

This will generate messages on a gaussian distribution with an average size each 512-bytes. The message sizes will
have a standard deviation of 100 bytes, and the size will only change every 100 messages.  The distribution of
messages will be as follows:

   The average size of the messages are 512 bytes.
   ~68% of the messages are between 412 and 612 bytes
   ~95% of the messages are between 312 and 712 bytes
   ~99% of the messages are between 212 and 812 bytes
trogdor/src/main/java/org/apache/kafka/trogdor/workload/GaussianTimestampRandomPayloadGenerator.java