switch to streaming mapred, to enable handling 100k objects
switch to streaming mapred, to enable handling 100k objects

Dell devtest box shows:

   10k objects: 29sec for list+fetch; 10sec for MR
  100k objects: 5.5min for list+fetch; 2.25min for MR with this patch;
                Erlang VM death (memory alloc) for MR without this patch

The memory alloc problem appears to be the garbage created by the use of
orddict:append_list/3 in riakc_pb_socket:wait_for_mapred/3.

laurenrother/riak_cs,basho/riak_cs,dragonfax/riak_cs,sdebnath/riak_cs,basho/riak_cs,GabrielNicolasAvellaneda/riak_cs,GabrielNicolasAvellaneda/riak_cs,sdebnath/riak_cs,yangchengjian/riak_cs,laurenrother/riak_cs,dragonfax/riak_cs,basho/riak_cs,GabrielNicolasAvellaneda/riak_cs,dragonfax/riak_cs,basho/riak_cs_lfs,yangchengjian/riak_cs,dragonfax/riak_cs,laurenrother/riak_cs,sdebnath/riak_cs,basho/riak_cs_report,sdebnath/riak_cs,yangchengjian/riak_cs,yangchengjian/riak_cs,laurenrother/riak_cs,basho/riak_cs,GabrielNicolasAvellaneda/riak_cs