We're deprecating the IRC channel (#7)

Replacing it with Slack

CONTRIBUTING.md

@@ -47,7 +47,7 @@ Some things to note that aren't immediately obvious to folks just starting out:
 2. Any changes you make on your branch that you used for one PR will automatically appear in another PR so if you have more than 1 PR, be sure to always create different branches for them.
 3. Weird things happen with commit history if you don't create your PR branches off of `master` so always make sure you have the `master` branch checked out before creating a branch for a PR
 
-If you feel overwhelmed at any point, don't worry, it can be a lot to learn when you get started. You can usually find me on the [Pony IRC](https://webchat.freenode.net/?channels=%ponylang) if you need help.
+If you feel overwhelmed at any point, don't worry, it can be a lot to learn when you get started. You can usually find me on the [Pony Slack](https://www.ponylang.io/get-slack-invite) if you need help.
 
 You can get help using GitHub via [the official documentation](https://help.github.com/). Some hightlights include: