pix2pix integration issues

[gregbugaj]

In find_model_using_name there is an issue with the dynamic imports.

    model_filename = "models." + model_name + "_model"
    modellib = importlib.import_module(model_filename)

Workaround is to have them map directly

    # FIXME : this needs to be fixes as the import_module is not working
    mapping = {
        'test': TestModel,
        'base': BaseModel
    }

    return mapping[model_name]

I suspect this is due to nested model folder names being imported.