Python Support

It would be useful if I could specify packages that should not be synced.

Why might I disinclude packages from a sync?

• Known security problems for some versions
• typo-squatting prevention/cleanup (like `requirements.txt`)
• I don't need the wheels for that type of linux distribution (probably should be a separate issue)

Blacklists should work alongside whitelists

Something like:
inventory = set(whitelist) - set(blacklist)

Ideally, the blacklist will use the same structure as whitelist, so the user could blacklist by name, by version, by version range, hash, etc.