--cache, home: Use convenience methods to load formulae and casks

[whoiswillma]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

Small refactoring change. Instead of loading formulae and casks manually, use convenience methods that already exist on CLI::Args to load formulae and casks.

[MikeMcQuaid]

A couple of tweaks!

[MikeMcQuaid]

Thanks again @whoiswillma!