Added Ruby and Sass to requirements with install directions

Author: tatethurston

README.md

@@ -19,6 +19,7 @@ Before you begin we recommend you read about the basic building blocks that asse
 Make sure you have installed all of the following prerequisites on your development machine:
 * Node.js - [Download & Install Node.js](https://nodejs.org/en/download/) and the npm package manager. If you encounter any problems, you can also use this [GitHub Gist](https://gist.github.com/isaacs/579814) to install Node.js.
 * MongoDB - [Download & Install MongoDB](http://www.mongodb.org/downloads), and make sure it's running on the default port (27017).
+* Ruby - [Download & Install Ruby](https://www.ruby-lang.org/en/documentation/installation/)
 * Bower - You're going to use the [Bower Package Manager](http://bower.io/) to manage your front-end packages. Make sure you've installed Node.js and npm first, then install bower globally using npm:
 
 ```bash
@@ -31,6 +32,12 @@ $ npm install -g bower
 $ npm install -g grunt-cli
 ```
 
+* Sass - You're going to use [Sass](http://sass-lang.com/) to compile CSS during your grunt task. Make sure you have ruby installed, and then install Sass using gem install:
+
+```bash
+$ gem install sass
+```
+
 ## Downloading MEAN.JS
 There are several ways you can get the MEAN.JS boilerplate: