Replace gitter with slack

Author: szilvihorvath

ruby/lesson2/tutorial.md

@@ -238,7 +238,7 @@ rake regen
 
 To try out the koans run `rake`. It gives you a hint as to what fails and you can move forward by fixing the file and running `rake` again.
 
-If you are working through this at home you can ask for help in our [gitter channel](https://gitter.im/codebar/tutorials).
+If you are working through this at home you can ask for help in our [slack channel](https://slack.codebar.io/).
 
 ## Some reading material
 

ruby/lesson4/tutorial.md

@@ -9,7 +9,7 @@ There are no sample files for this tutorial as you should already know how to cr
 
 Don't forget to commit to git regularly and also try to **type** out the examples as much as possible instead of copy & pasting!
 
-If you are going through the tutorial in your own time and need any help then [join the chatroom](https://gitter.im/codebar/tutorials), but first read our [Code of Conduct](http://codebar.io/code-of-conduct) as we will not tolerate any inappropriate behavior.
+If you are going through the tutorial in your own time and need any help then [join our slack channel](https://slack.codebar.io/), but first read our [Code of Conduct](http://codebar.io/code-of-conduct) as we will not tolerate any inappropriate behavior.
 
 # What is Object Oriented Programming?
 

ruby/lesson5/tutorial.md

@@ -7,7 +7,7 @@ In today's tutorial, we will be again going through OO concepts - some of which
 
 Don't forget to commit to git regularly and also try to **type** out the examples as much as possible instead of copy & pasting!
 
-If you are going through the tutorial in your own time and need any help then [join the chatroom](https://gitter.im/codebar/tutorials), but first read our [Code of Conduct](http://codebar.io/code-of-conduct) as we will not tolerate any inappropriate behavior.
+If you are going through the tutorial in your own time and need any help then [join the slack channel](https://slack.codebar.io/), but first read our [Code of Conduct](http://codebar.io/code-of-conduct) as we will not tolerate any inappropriate behavior.
 
 # How does inheritance fit in OO?