Remove Cask Gemfile.

Library/Homebrew/cask/Gemfile

-source "https://rubygems.org"
-
-gem "parallel_tests"
-gem "rspec"
-gem "rspec-its", require: false
-gem "rspec-wait", require: false
-
-group :coverage do
-  gem "simplecov", require: false
-  gem "codecov", require: false
-end

Library/Homebrew/cask/Gemfile.lock

-GEM
-  remote: https://rubygems.org/
-  specs:
-    codecov (0.1.9)
-      json
-      simplecov
-      url
-    diff-lcs (1.3)
-    docile (1.1.5)
-    json (2.0.3)
-    parallel (1.10.0)
-    parallel_tests (2.13.0)
-      parallel
-    rspec (3.5.0)
-      rspec-core (~> 3.5.0)
-      rspec-expectations (~> 3.5.0)
-      rspec-mocks (~> 3.5.0)
-    rspec-core (3.5.4)
-      rspec-support (~> 3.5.0)
-    rspec-expectations (3.5.0)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.5.0)
-    rspec-its (1.2.0)
-      rspec-core (>= 3.0.0)
-      rspec-expectations (>= 3.0.0)
-    rspec-mocks (3.5.0)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.5.0)
-    rspec-support (3.5.0)
-    rspec-wait (0.0.9)
-      rspec (>= 3, < 4)
-    simplecov (0.13.0)
-      docile (~> 1.1.0)
-      json (>= 1.8, < 3)
-      simplecov-html (~> 0.10.0)
-    simplecov-html (0.10.0)
-    url (0.3.2)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  codecov
-  parallel_tests
-  rspec
-  rspec-its
-  rspec-wait
-  simplecov
-
-BUNDLED WITH
-   1.14.5