Cask: fixes for quarantining

Gatekeeper's Path Randomization is currently making automated
installation a nightmare. Let's manually toggle the (undocumented) app
translocation bit in the `com.apple.quarantine` extended attribute.

While we're at it, let's also toss in some fixes:

- zip downloads with improper permissions that prevent us from
quarantining
- quarantine/release/skip downloads as requested by the user