Fix install script to use unzip for zip files

[lockmeister]

Substituted "unzip" for "tar" in the install script.

This fixes this error which I got when running the install script:

tar: This does not look like a tar archive
tar: Skipping to next header
tar: Archive contains ‘d$@i\203\304\bL’ where numeric mode_t value expected
tar: Archive contains ‘dH3\004%(\0\0\0\017\205\335’ where numeric time_t value expected
tar: Archive contains ‘9d$(\017\205\021\377’ where numeric uid_t value expected
tar: Archive value -169126968458240 is out of gid_t range 0..4294967295
tar: $PH��$�: implausibly old time stamp 1970-01-01 11:59:59
tar: Skipping to next header
tar: Exiting with failure status due to previous errors

[benfdking]

That was some copy pasta 🍝 on our behalf. Thanks for the contribution! Just running it and testing.