cask --cache: Deprecate command

[whoiswillma]

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Add a TODO to deprecate brew cask --cache for the next release (and sneak a TODO for brew cask home as well).

Since calling odeprecated in tests throws an exception, modify the tests such that they pass to avoid failing a lot of tests when the deprecation is enabled.

[MikeMcQuaid]

Thanks for handling the deprecation warnings in advance!

[MikeMcQuaid]

Thanks again @whoiswillma!