Update chapter filter logic

The previous way was inlining errors on GitHub...

Author: Mike Moore

chapters/index.html

@@ -6,16 +6,16 @@ <h1>Chapter Index</h1>
 <h2>Working with Strings</h2>
 {% for page in site.pages %}
 <ul>
-  {% if page.categories contains 'strings' %}
+  {% if page.url contains '/chapters/strings/' %}
     <li><a href="{{ page.url }}">{{ page.title }}</a></li>
   {% endif %}
 </ul>
 {% endfor %}
 <h2>Working with Arrays</h2>
 {% for page in site.pages %}
 <ul>
-  {% if page.categories contains 'arrays' %}
+  {% if page.url contains '/chapters/arrays/' %}
     <li><a href="{{ page.url }}">{{ page.title }}</a></li>
   {% endif %}
 </ul>
-{% endfor %}
+{% endfor %}

index.html

@@ -17,15 +17,15 @@ <h1>CoffeeScript Cookbook</h1>
 <h2>Working with Strings</h2>
 {% for page in site.pages %}
 <ul>
-  {% if page.categories contains 'strings' %}
+  {% if page.url contains '/chapters/strings/' %}
     <li><a href="{{ page.url }}">{{ page.title }}</a></li>
   {% endif %}
 </ul>
 {% endfor %}
 <h2>Working with Arrays</h2>
 {% for page in site.pages %}
 <ul>
-  {% if page.categories contains 'arrays' %}
+  {% if page.url contains '/chapters/arrays/' %}
     <li><a href="{{ page.url }}">{{ page.title }}</a></li>
   {% endif %}
 </ul>