readme.MD and contributing.MD review (#50)

* readme.MD and contributing.MD review

- Adds a blurb about forking repo for first time contributors
- Add link to github’s description of code fencing

* add a comma

Author: jaredgalanis

CONTRIBUTING.md

@@ -79,7 +79,7 @@ In code samples:
 * Follow the [Ember Style Guide](https://github.com/emberjs/ember.js/blob/master/STYLEGUIDE.md).
 * Use double-quotes in templates, i.e., `<div class="awesome">{{foo-bar title="Tomster"}}</div>`.
 * Omit the boilerplate that Ember CLI generates, especially the `import Ember from 'ember'` at the top of every file.
-* In fenced code blocks, write paths relative to the project root. e.g., `app/router.js`, `config/environment.js`
+* In [fenced code blocks](https://help.github.com/articles/creating-and-highlighting-code-blocks/), write paths relative to the project root. e.g., `app/router.js`, `config/environment.js`
 * When writing a fenced code block with a filename, do so by writing the language name first followed by the file name within a data-filename block as shown below,
 
 \`\`\` javascript {data-filename="app/router.js"}

README.md

@@ -39,6 +39,12 @@ computer. This repository, `guides-source` contains only written content
 as markdown files, which are fetched and displayed by
 [guides-app](https://github.com/ember-learn/guides-app).
 
+Before following the below instructions and making any changes, first-time
+contributors should see [CONTRIBUTING.md](CONTRIBUTING.md) for
+instructions on forking the `guides-source` and `guides-app`
+repositories and making a first pull
+request.
+
 ```sh
 git clone git://github.com/ember-learn/guides-app.git
 git clone git://github.com/ember-learn/guides-source.git