Add batching statistics

[symbiont-stevan-andjelkovic]

When the benchmarks from the Java version is run they print:

Run 0, Disruptor=23,640,661 ops/sec BatchPercent=71.01% AverageBatchSize=3
Run 1, Disruptor=24,479,804 ops/sec BatchPercent=69.37% AverageBatchSize=3
Run 2, Disruptor=25,380,710 ops/sec BatchPercent=67.20% AverageBatchSize=3
Run 3, Disruptor=26,525,198 ops/sec BatchPercent=67.41% AverageBatchSize=3
...

Those batching statistics could be interesting to have.