hbc/qualified_token: use regex captures instead of String#split

Library/Homebrew/cask/lib/hbc/qualified_token.rb

@@ -2,10 +2,8 @@ module Hbc
   module QualifiedToken
     def self.parse(arg)
       return nil unless arg.is_a?(String)
-      return nil unless arg.downcase =~ HOMEBREW_TAP_CASK_REGEX
-      # eg caskroom/cask/google-chrome
-      # per https://github.com/Homebrew/brew/blob/master/docs/brew-tap.md
-      user, repo, token = arg.downcase.split("/")
+      return nil unless match = arg.downcase.match(HOMEBREW_TAP_CASK_REGEX)
+      user, repo, token = match.captures
       odebug "[user, repo, token] might be [#{user}, #{repo}, #{token}]"
       [user, repo, token]
     end