RestClient renamed poolsize key

RestClient does not have POOL_SIZE_KEY anymore.
From the source it is probably renamed to HTTP_POOL_SIZE.
The previous constant value was poolsize and the new constant
is http.poolsize.

Upgrading the R2, Data, Pegasus libraries along with this change.
Merge pull request #194 from arunthirupathi/PoolSizeRename

RestClient renamed poolsize key