Remove refs to the Freenode IRC channel

It's gone out of fashion for at least a couple of years.

CONTRIBUTING.md

@@ -1,12 +1,10 @@
 # Contributing and Reporting
 
 This is the issue tracker for Opal. If you have a more general question about
-using Opal (or related libraries) then use the [stackoverflow tag (#opalrb)][SO], the
-[#opal][freenode] irc channel on *FreeNode*, or the *Gitter* chatroom at [opal/opal][gitter]
+using Opal (or related libraries) then use the [stackoverflow tag (#opalrb)][SO], or the *Gitter* chatroom at [opal/opal][gitter]
 (also available as IRC at `irc.gitter.im`).
 
 [SO]: http://stackoverflow.com/questions/ask?tags=opalrb
-[freenode]: http://webchat.freenode.net/?channels=opal
 [gitter]: https://gitter.im/opal/opal
 
 What follows is a quick checklist you can before sending issues or pull-requests, for in-depth instructions on how to hack the internals of Opal and setup the development environment please see [`HACKING.md`][hacking].
@@ -38,7 +36,7 @@ What follows is a quick checklist you can before sending issues or pull-requests
 4.  Add a Changelog entry at the top of `CHANGELOG.md`
 
 
-### A note on commits in PR
+### A note on commits in PRs
 
 You could be asked to squash your commits during a PR review. That doesn't mean there's a preference for a single commit for each PR, rather it's a request to have each commit focused on a specific group changes and avoid the sequence of changes, fixups and reverts that tell an interesting story but in the end make the use of `git blame` quite difficult.
 

README.md

@@ -10,7 +10,7 @@
 Opal is a Ruby to JavaScript source-to-source compiler. It also has an
 implementation of the Ruby corelib.
 
-Opal is [hosted on GitHub](https://github.com/opal/opal). Chat is available on *Gitter* at [opal/opal](https://gitter.im/opal/opal) (also available as IRC at `irc.gitter.im`) and the Freenode IRC channel at [#opal](https://webchat.freenode.net/?channels=opal).
+Opal is [hosted on GitHub](https://github.com/opal/opal). Chat is available on *Gitter* at [opal/opal](https://gitter.im/opal/opal) (also available as IRC at `irc.gitter.im`).
 Ask questions on [stackoverflow (tag #opalrb)](https://stackoverflow.com/questions/ask?tags=opalrb). Get the [Opalist newsletter](http://opalist.co) for updates and community news.
 
 [![Inline docs](https://inch-ci.org/github/opal/opal.svg?branch=master&style=flat)](https://opalrb.com/docs)