As noted in #12, #14, #15, #16, #17, and even way back in a comment on
a5fb55b4, my prior inclination to try to
use `:included_applications` and `:applications` separately was
ill-fated. Under Elixir 1.9.0, Mix started blowing up properly on `mix
release` with

  ** (Mix) :combine is listed both as a regular application and as an
  included application

So I guess everything should go under `:applications` by design. /shrug

I'm trusting this to be backwards-compatible with Elixir 1.3, per the
discussions on #1 from way back when. 😅