Update markdown to use absolute image paths, fixing broken images

site/dev/tools/markdown.md

 Markdown
 ========
 
 This site can handle normal MarkDown and many common extensions. To learn
 how the following is done please see the [source for this page](./markdown.md).
 Any file you put under `/site/` that has the extension `.md` will be processed
 as MarkDown. All other files will be served directly. For example, images
 can be added and they will be served correctly and referenced from within MarkDown files.
 
 When preparing for a code review of site docs you can get a preview of how the
@@ skipping 53 matching lines @@
 1. First
 2. Second:
   * Fee
     * Fie
       * Foe
   * Fum
 3. Third
 
 Incorporate images:
 
-![image](image.png)
+![image](/dev/tools/image.png)
 
 Or go old school and use [ASCII art](http://asciiflow.com/):
 
 ~~~~
 
        +----------------+
        |  Should you    |
     +--+ use ASCII art? +--+
     |  +----------------+  |
     |                      |
@@ skipping 327 matching lines @@
 
 Output:
 
     <p>If you want your page to validate under XHTML 1.0 Strict,
     you've got to put paragraph tags in your blockquotes:</p>
     
     <pre><code>&lt;blockquote&gt;
         &lt;p&gt;For example.&lt;/p&gt;
     &lt;/blockquote&gt;
     </code></pre>