tup v0.7.9 released

[Mike Shal]

Hi all, I've tagged v0.7.9 in tup. Notable changes since v0.7.8 include:

 - FreeBSD improvements (thanks Jose!)
 - macOS 10.15 support
 - !tup_preserve (to copy src files into variants) should now work
 - Progress toward better parallelism during the update phase

Please post if you notice any issues while upgrading!

Thanks,

-Mike