Appends with no returns and few errors can break deserialization

[jsbali]

If a batch contains 4 appends with return_result as false and last two fail which can due to multiple reasons say the region was moved or was unavailable.

Then the response returned by hbase will contain only two ResultOrException elements with index say 2 and 3 (batch size 4).
Deserializing the above will throw up on
https://github.com/OpenTSDB/asynchbase/blob/master/src/MultiAction.java#L627 because we don't do a bounds check and will receive an IndexOutOfBoundsException.

The simplest fix can be to add a bounds check for both n < batch.size() and n!=index.
But I may be missing some things so need your attention.