Refactor PitmanYor::Mixture
Fix assertions in protobuf_stream.hpp
Add protobuf serialization for dbg.*.Group
Add ProtobufSerializable mixin
Add assertion to protobuf::OutFile::write
Refactor for safer protobuf streams; add ROOT
Refactor Scorer and Sampler as objects.
Rename classifier to mixture.
Sort the same way on linux and osx.