diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 000000000..279f92392
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,81 @@
+# Developer notes
+
+## Starting a local instance
+
+This is a mere Jekyll site, and `bundle exec jekyll serve` should be fine. But I suggest you use this instead:
+
+```
+make
+```
+
+## CSS classes
+
+`h2` supports these:
+
+    {: .-two-column}
+    {: .-three-column}
+    {: .-wide-second}       # combine with -xxx-column
+    {: .-left-reference}
+
+`h3` supports these:
+
+    {: .-prime}
+
+`table` supports these:
+
+    {: .-shortcuts}
+    {: .-left-align}
+    {: .-headers}
+
+`pre` supports these:
+
+    {: .-setup}
+    {: .-box-chars}
+
+`ul` supports these:
+
+    {: .-also-see}
+    {: .-four-column}
+    {: .-six-column}
+
+## Frontmatter
+
+Each sheet supports these metadata:
+
+```yml
+---
+title: React.js
+layout: 2017/sheet   # 'default' | '2017/sheet'
+
+# Optional:
+category: React
+updated: 2017-08-30       # To show in the updated list
+ads: false                # Add this to disable ads
+weight: -5                # lower number = higher in related posts list
+deprecated: true          # Don't show in related posts
+prism_languages: [vim]    # Extra syntax highlighting
+---
+```
+
+## Prism languages
+
+For supported prism languages:
+
+- <https://github.com/PrismJS/prism/tree/gh-pages/components>
+
+## Setting up redirects
+
+This example sets up a redirect from `es2015` to `es6`:
+
+```yml
+# /es2015.md
+---
+title: ES2015
+category: Hidden
+redirect_to: /es6
+---
+```
+
+## Localizations
+
+See `_data/content.yml` for chrome strings.
diff --git a/Gemfile b/Gemfile
index 053c27dc3..37f5eaa42 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,2 +1,2 @@
 source 'https://rubygems.org'
-gem 'github-pages'
+gem 'github-pages', group: :jekyll_plugins
diff --git a/Readme.md b/Readme.md
index 50092d44a..f9226cc50 100644
--- a/Readme.md
+++ b/Readme.md
@@ -14,84 +14,4 @@
 
 ---
 
-# Dev notes
-
-## Starting a local instance
-
-This is a mere Jekyll site, and `bundle exec jekyll serve` should be fine. But I suggest you use this instead:
-
-```
-make
-```
-
-## CSS classes
-
-`h2` supports these:
-
-    {: .-two-column}
-    {: .-three-column}
-    {: .-wide-second}       # combine with -xxx-column
-    {: .-left-reference}
-
-`h3` supports these:
-
-    {: .-prime}
-
-`table` supports these:
-
-    {: .-shortcuts}
-    {: .-left-align}
-    {: .-headers}
-
-`pre` supports these:
-
-    {: .-setup}
-    {: .-box-chars}
-
-`ul` supports these:
-
-    {: .-also-see}
-    {: .-four-column}
-    {: .-six-column}
-
-## Frontmatter
-
-Each sheet supports these metadata:
-
-```yml
----
-title: React.js
-layout: 2017/sheet   # 'default' | '2017/sheet'
-
-# Optional:
-category: React
-updated: 2017-08-30       # To show in the updated list
-ads: false                # Add this to disable ads
-weight: -5                # lower number = higher in related posts list
-deprecated: true          # Don't show in related posts
-prism_languages: [vim]    # Extra syntax highlighting
----
-```
-
-## Prism languages
-
-For supported prism languages:
-
-- <https://github.com/PrismJS/prism/tree/gh-pages/components>
-
-## Setting up redirects
-
-This example sets up a redirect from `es2015` to `es6`:
-
-```yml
-# /es2015.md
----
-title: ES2015
-category: Hidden
-redirect_to: /es6
----
-```
-
-## Localizations
-
-See `_data/content.yml` for chrome strings.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for developer notes.
diff --git a/_config.yml b/_config.yml
index dc4720159..9aa346aa2 100644
--- a/_config.yml
+++ b/_config.yml
@@ -13,6 +13,7 @@ plugins:
 exclude:
   - Makefile
   - README.md
+  - CONTRIBUTING.md
   - Gemfile
   - Gemfile.lock
   - CNAME