I'm pretty sure it's buried somewhere in his manifest/cask file.

https://gist.github.com/gnufied/7160410

Looks like it says: (depends-on "color-theme-sanityinc-tomorrow") ... (depends-on "noctilux-theme") ... (depends-on "soft-morning-theme")

Sorry, I didn't look into those, but saw he didn't respond. Good luck!