Adding limit when copying elements from queue to collection

[binhnv]

I am testing storm and cassandra using this library and I notice that when the input is increased the process latency also increased. I checked our cassandra cluster's statistic and I don't see any write latency issue so I think the time it spends is to copy from queue to array. I looked at the code and it is using drainTo method to copy all available elements from the queue to collection. If there are many elements in the queue then:

• It takes longer to copy elements to collection
• There will be chance of out of memory. Because of this I suggest to change the code so that caller can set maximum number of items it want to copy.

[binhnv]

There is an implementation for this here https://github.com/ptgoetz/storm-cassandra/pull/7