Bump riak_pb dependency to 1.4.0.4.
Bump riak_pb dependency to 1.4.0.4.

groovenauts-erlang/riak-erlang-client,pma/riak-erlang-client,esl/riak-erlang-client,rhumbertgz/riak-erlang-client,inaka/riak-erlang-client,SiftLogic/riak-erlang-client,linearregression/riak-erlang-client,jmayfield74/riak-erlang-client,paulperegud/riak-erlang-client,GabrielNicolasAvellaneda/riak-erlang-client