Not documented(?): Doesn't block mounting at re-start

[dsbos]

I don't know if Disk Arbitrator is intended to block the auto-mounting that usually happens when a Mac is restarted, but it doesn't do so, and that fact doesn't seem to be documented in https://github.com/aburgh/Disk-Arbitrator/blob/master/README.markdown.

That fact should probably be documented (so users know to detach any external disks before restarting if they want the usual protection that Disk Arbitrator provides).