Merge pull request #127 from abeykoon/fix_message_delivery_after_trackerChange

fixed message reject and requeuing with new tracker.
Merge pull request #128 from abeykoon/fix_message_delivery_after_trackerChange_02

Fixed ack handling problem thro disruptor.
Get absolute value when resolving the slot Id.
Merge pull request #129 from akalankapagoda/GetAbsSlotId

Get absolute value when resolving the slot Id.
fix issue of ack receive not decrementing slot message count.