Add missing :cask metadata to specs.

Library/Homebrew/test/cask/cli/doctor_spec.rb

@@ -1,6 +1,4 @@
-require "hbc/version"
-
-describe Hbc::CLI::Doctor do
+describe Hbc::CLI::Doctor, :cask do
   it "displays some nice info about the environment" do
     expect {
       Hbc::CLI::Doctor.run

Library/Homebrew/test/cask/cli/style_spec.rb

@@ -2,7 +2,7 @@ require "English"
 require "open3"
 require "rubygems"
 
-describe Hbc::CLI::Style do
+describe Hbc::CLI::Style, :cask do
   let(:args) { [] }
   let(:cli) { described_class.new(args) }
 

Library/Homebrew/test/cask/dsl/stanza_proxy_spec.rb

@@ -1,4 +1,4 @@
-describe Hbc::DSL::StanzaProxy do
+describe Hbc::DSL::StanzaProxy, :cask do
   let(:stanza_proxy) {
     described_class.new(Array) { [:foo, :bar, :cake] }
   }

Library/Homebrew/test/cask/dsl/version_spec.rb

@@ -1,4 +1,4 @@
-describe Hbc::DSL::Version do
+describe Hbc::DSL::Version, :cask do
   shared_examples "expectations hash" do |input_name, expectations|
     expectations.each do |input_value, expected_output|
       context "when #{input_name} is #{input_value.inspect}" do

Library/Homebrew/test/cask/macos_spec.rb

@@ -1,4 +1,4 @@
-describe MacOS do
+describe MacOS, :cask do
   it "says '/' is undeletable" do
     expect(MacOS).to be_undeletable(
       "/",

Library/Homebrew/test/cask/verify/checksum_spec.rb

@@ -1,4 +1,4 @@
-describe Hbc::Verify::Checksum do
+describe Hbc::Verify::Checksum, :cask do
   let(:cask) { double("cask") }
   let(:downloaded_path) { double("downloaded_path") }
   let(:verification) { described_class.new(cask, downloaded_path) }