cask style: fix --fix

[commitay]

• 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?

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cc @reitermarkus

$ brew cask style -vd --fix metasploit
warning: parser/current is loading parser/ruby23, which recognizes
warning: 2.3.5-compliant syntax, but you are running 2.3.3.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
-P/--parallel can not be combined with --auto-correct.

[reitermarkus]

Thanks!