Ruby 2.4.1 doc update

Gemfile

@@ -1,10 +1,10 @@
 source 'https://rubygems.org'
 
 ## If you update the version here, also update it in .travis.yml and
-## README.md. Then push your branch and make sure Travis supports that
-## version. Then remind one of the site maintainers that they need to
-## run `rvm install <VERSION>` on the build server(s) before they commit
-## to master
+## docs/setting-up-your-environment.md. Then push your branch and
+## make sure Travis supports that version. Then remind one of the
+## site maintainers that they need to run `rvm install <VERSION>` on
+## the build server(s) before they commit to master
 ruby '2.4.1'
 
 ## Used on the build server. If you add a package here (like nokogiri)
@@ -14,8 +14,6 @@ ruby '2.4.1'
 ## your dependencies, then nothing extra needs to be done
 group :development do
   gem 'ffi-icu'
-  ## When we upgrade to Jekyll 3.0.0 or higher, remove
-  ## _plugin/remove-html-extension.rb
   gem 'jekyll', '~>3.0'
   gem 'json', '>= 1.9'
   gem 'less', '2.4.0'

docs/setting-up-your-environment.md

@@ -42,19 +42,19 @@ following command:
 
     source ~/.rvm/scripts/rvm
 
-**Install Ruby 2.0.0**
+**Install Ruby 2.4.1**
 
-To install Ruby 2.0.0, simply run this command:
+To install Ruby 2.4.1, simply run this command:
 
-    rvm install ruby-2.0.0
+    rvm install 2.4.1
 
 Sometimes this will find a pre-compiled Ruby package for your Linux
 distribution, but sometimes it will need to compile Ruby from scratch
 (which takes about 15 minutes).
 
-After Ruby 2.0.0 is installed, make it your default Ruby:
+After Ruby 2.4.1 is installed, make it your default Ruby:
 
-    rvm alias create default ruby-2.0.0
+    rvm alias create default ruby-2.4.1
 
 And tell your system to use it: