Modify slack invitation link

js/lesson8/tutorial.md

@@ -9,7 +9,7 @@ Ask your coach for help on getting your project setup in Github and granting per
 
 Today's session is not aimed to teach you anything new programming-wise but to enable you to start building things on your own. You are not expected to produce a working application by the end of today's lesson but to structure your thoughts and figure out what you want to build.
 
-To get help outside of our sessions go to [the Slack channel here](https://codebar.slack.com/messages/general/details/). If you are not on Slack, use [this link](https://codebar-slack.herokuapp.com/) to get an invite.
+To get help outside of our sessions go to [the Slack channel here](https://codebar.slack.com/messages/general/details/). If you are not on Slack, use [this link](https://slack.codebar.io/) to get an invite.
 
 You can also send an email to [[email protected]](mailto:[email protected]).