Add TODO list support for Blackfriday

* Add CSS class to TODO list and list items
* Add a flag to turn task list support off

Fixes #2269

content/content/markdown-extras.md

@@ -0,0 +1,49 @@
+---
+aliases:
+- /doc/supported-formats/
+lastmod: 2016-07-22
+date: 2016-07-22
+menu:
+  main:
+    parent: content
+prev: /content/summaries
+next: /content/example
+title: Markdown Extras
+weight: 66
+toc: false
+---
+
+Hugo provides some convenient markdown extensions.
+
+## Task lists
+
+Hugo supports GitHub styled task lists (TODO lists) for the Blackfriday renderer (md-files). See [Blackfriday config](/overview/configuration/#configure-blackfriday-rendering) for how to turn it off.
+
+Example:
+
+```markdown
+- [ ] a task list item
+- [ ] list syntax required
+- [ ] incomplete
+- [x] completed
+```
+
+Renders as:
+
+- [ ] a task list item
+- [ ] list syntax required
+- [ ] incomplete
+- [x] completed
+
+
+And produces this HTML:
+
+```html
+
+<ul class="task-list">
+<li><input type="checkbox" disabled="" class="task-list-item"> a task list item</li>
+<li><input type="checkbox" disabled="" class="task-list-item"> list syntax required</li>
+<li><input type="checkbox" disabled="" class="task-list-item"> incomplete</li>
+<li><input type="checkbox" checked="" disabled="" class="task-list-item"> completed</li>
+</ul>
+```

content/content/summaries.md

@@ -4,9 +4,9 @@ date: 2013-07-01
 menu:
   main:
     parent: content
-next: /content/example
 notoc: true
 prev: /content/ordering
+next: /content/markdown-extras
 title: Summaries
 weight: 65
 ---

content/overview/configuration.md

@@ -1,14 +1,14 @@
 ---
 aliases:
 - /doc/configuration/
-lastmod: 2015-12-08
+lastmod: 2016-07-22
 date: 2013-07-01
 linktitle: Configuration
 menu:
   main:
     parent: getting started
 next: /overview/source-directory
-notoc: true
+toc: true
 prev: /overview/usage
 title: Configuring Hugo
 weight: 40
@@ -195,6 +195,18 @@ But Hugo does expose some options---as listed in the table below, matched with t
 </thead>
 
 <tbody>
+
+<tr>
+<td><code><strong>taskLists</strong></code></td>
+<td><code>true</code></td>
+<td><code></code></td>
+</tr>
+<tr>
+<td class="purpose-title">Purpose:</td>
+<td class="purpose-description" colspan="2">Turn off GitHub styled automatic task/TODO list generation.
+</td>
+</tr>
+
 <tr>
 <td><code><strong>smartypants</strong></code></td>
 <td><code>true</code></td>