Convert brew --version test to spec.

Library/Homebrew/test/cmd/--version_spec.rb

@@ -0,0 +1,8 @@
+describe "brew --version", :integration_test do
+  it "prints the Homebrew version" do
+    expect { brew "--version" }
+      .to output(/^Homebrew #{Regexp.escape(HOMEBREW_VERSION.to_s)}\n/).to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+  end
+end

Library/Homebrew/test/version_test.rb

@@ -1,8 +0,0 @@
-require "testing_env"
-
-class IntegrationCommandTestVersion < IntegrationCommandTestCase
-  def test_version
-    assert_match HOMEBREW_VERSION.to_s,
-                 cmd("--version")
-  end
-end