Add RVM notes for ruby.

I'd rather not have anyone left in Ruby version or
dependency hell. Here's hoping this saves us all!

README.md

@@ -6,13 +6,43 @@ and [creating pages](https://jekyllrb.com/docs/pages/).
 
 # Quickstart
 
-- Install Ruby if it's not already on your system
+In order to not blow up your computer handling a system wide Ruby installation, it is
+advised that you use [RVM](https://rvm.io/rvm/install). Once you've got that installed
+and configured, get the latest version of Ruby with:
 
+```bash
+$ rvm install 2.4.2
 ```
-gem install jekyll bundler
+
-jekyll serve
+Select that version and then create an isolated [gemset](https://rvm.io/gemsets/basics) with:
+
+```bash
+$ rvm use 2.4.2
+$ rvm gemset create autonomic
 ```
-- Edit `.md` files under `src` and `src/_posts`.
+
+Then you can get your Ruby dependencies installed with:
+
+``` bash
+$ gem install jekyll bundler
+```
+
+And serve the website locally with:
+
+``` bash
+$ jekyll serve
+```
+
+You can edit content in the `.md` files under `src` and `src/_posts`.
+
+When you're hacking later on (or in a new shell), you'll need to run:
+
+``` bash
+$ rvm use 2.4.2
+$ rvm gemset use autonomic
+```
+
+And then you'll have access to the environment.
 
 # Credits