Fix w/ a test

lib/linguist/language.rb

@@ -585,6 +585,7 @@ module Linguist
       :aliases           => options['aliases'],
       :tm_scope          => options['tm_scope'],
       :ace_mode          => options['ace_mode'],
+      :codemirror_mode   => options['codemirror_mode'],
       :wrap              => options['wrap'],
       :group_name        => options['group'],
       :searchable        => options.fetch('searchable', true),

test/test_language.rb

@@ -349,6 +349,10 @@ class TestLanguage < Minitest::Test
     assert Language.ace_modes.include?(Language['FORTRAN'])
   end
 
+  def test_codemirror_mode
+    assert_equal 'clike', Language['C++'].codemirror_mode
+  end
+
   def test_wrap
     assert_equal false, Language['C'].wrap
     assert_equal true, Language['Markdown'].wrap