Adding Photoshop CC

Ok, so this is a working cask, but I'm also looking for some guidance on how to make express things a bit more nicely:

* Line 2: Can I create arbitrary variables which I reference later using #{}? It doesn't seem to work, but I'm not sure if it is supposed to
*Line 3: Is there a way to specify options for casks? With the Adobe apps you can't dynamically switch languages, so you want the user to specify which locale they want to install.
*Line 12: The Installer needs a specific xml file which is inside the volume. How do I reference the path of the mounted volume w/o hardcoded strings? I tried using `#{staged_path}` but that gave me an error