title: Slack Api response shows encoded characters for Japanese characters in message
body: <p>I am using Slack API /channels.history to get messages of channel. My messages have Japanese characters. Api response is always encoded for Japanese characters as below:</p>
  
  <p>Original message in Slack web interface:</p>
  
  <pre><code>me: テスト
  </code></pre>
  
  <p>But It returns response:</p>
  
  <pre><code>{...
  'text': '\u30c6\u30b9\u30c8',
  }
  </code></pre>
  
  <p>I don't know which encoding method is used here. Then, how can I get Japanese characters back from Api response.</p>