Merge pull request #301 from nodejsjp/yosuke-furukawa-patch-1

Update index.njk

Author: yosuke-furukawa

source/layout/index.njk

@@ -19,7 +19,7 @@
 
 <h2>Slack</h2>
 
-<a href="https://iojs-jp-slack.herokuapp.com/">Slack 参加はこちらから</a>
+<a href="https://join.slack.com/t/jsconfjp/shared_invite/zt-1j7fqgvbq-Qa334TtwwKWC1eJBrgJ3yQ">Slack 参加はこちらから</a>
 
 
 {% for eventFile in file.files %}