Fix gitalk that id was too long to create a issue tag.

[ElderJames]

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What kind of change does this PR introduce? (check one with "x")

• Bug fix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
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• No

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Description

修复gitalk的id过长导致无法创建评论框的问题。

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Verification steps

• 设定在2018-03-01之后的评论框使用md5加密的pathname作为id，之前已创建的还使用明文
• 这个时间之前的文章如果需要创建评论需要在文章头部加上gitalk:md5来强行使用md5
• 这个时间之后的已创建的评论框需要需要在文章头部加上gitalk: plaintext来强行使用明文

[cntanglijun]

@ElderJames 也可以使用原生 btoa base64 加密

var gitalk = new Gitalk({
        id: btoa(location.href).slice(0,32),
        clientID: '<%= theme.comment.gitalk_client_id %>',
        clientSecret: '<%= theme.comment.gitalk_client_secret %>',
        repo: '<%= theme.comment.gitalk_repo %>',
        owner: '<%= theme.comment.gitalk_owner %>',
        admin: ['<%= theme.comment.gitalk_owner %>'],
        // facebook-like distraction free mode
        distractionFreeMode: false
})

可以做一个 Gitalk 配置项，可以设置加密规则，加密后字符长度。:ghost:

[ElderJames]

@cntanglijun 感谢建议。不过作者貌似不想合并这个pr 😭

[cubesky]

对不起 我现在无法联系其他的合作开发者，无法进行合并操作，我们会尽快进行合并