Tarsnap: Added Dependency

Tarsnap requires OpenSSL. So far we’ve been linking Tarsnap to the system-supplied OpenSSL. Doing so kind of sucks, because Apple *still*, to my knowledge, hasn’t patched Mavericks for the vulnerabilities disclosed in OpenSSL 0.9.8 and later fixed by 0.9.8za. We should stop building software against the Apple provided OpenSSL generally, but particularly for security software like Tarsnap.