Remove reply_pid after reply. Update current_buffer_size.
Remove reply_pid after reply. Update current_buffer_size.

* Set reply_pid back to undefined after we reply
* Update the current_buffer_size when we get new data
* Add TODO about getting MaxBufferSize from app.config

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