model serialization

[kylebgorman]

before we can really do #3, we need to develop a way to serialize a model and associated information. I propose that a model object should consist of a directory (possibly packed into a zip file or a tarball w/ or w/o compression) with the following files:

• the config.yaml used to generate the model (which includes human-readable metadata like the target language, and the phoneset)
• hmmdefs
• vFloors
• macros