Model Archive should allow excluding dirs/files

[mikeobr]

It would be helpful if model-archiver could exclude directories or files when creating an archive.

Consider the use case given this file structure: models/ test/ mms_server.py build/ If I want to archive mms_server.py and models/ as is, my test files and build files will automatically get included in the archive, even if unnecessary. Being able to exlude test/ and build/ would help streamline the archiving process.