Merge pull request #250 from sviptzk/dev

F 修复某种情况下导致highlight没有第二个class名（plain）而导致的代码语言变为undefined

source/js/main.js

@@ -278,7 +278,7 @@ $(function () {
       var langNameIndex, langName
       $figureHighlight.each(function () {
         langNameIndex = langName = $(this).attr('class').split(' ')[1]
-        if (langNameIndex === 'plain') langName = 'Code'
+        if (langNameIndex === 'plain' || langNameIndex === undefined) langName = 'Code'
         $(this).find('.highlight-tools').append('<div class="code-lang">' + langName + '</div>')
       })
     }