You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allpages gapcontinue="TODOリスト" />
  </query-continue>
  <query>
    <pages>
      <page pageid="13" ns="0" title="Serfで通信要件が満たせているかを自動テスト(Serverspecのように)してみようという試み">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">試み始めたとこ！なう中</rev>
        </revisions>
      </page>
      <page pageid="19" ns="0" title="SerfとGlusterFSでScalableな共有ディスクを作る">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">「SerfとGlusterFSでScalableな共有ディスクを作る」を作成中</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>