Render API Blueprint as Markdown

lib/github/markup/markdown.rb

@@ -25,7 +25,7 @@ class Markdown < Implementation
       }
 
       def initialize
-        super(/md|mkdn?|mdwn|mdown|markdown|litcoffee/)
+        super(/md|mkdn?|mdwn|mdown|markdown|litcoffee|apib/)
       end
 
       def load

test/markup_test.rb

@@ -37,6 +37,7 @@ def test_knows_what_it_can_and_cannot_render
     assert_equal true, GitHub::Markup.can_render?('README.markdown')
     assert_equal false, GitHub::Markup.can_render?('README.cmd')
     assert_equal true, GitHub::Markup.can_render?('README.litcoffee')
+    assert_equal true, GitHub::Markup.can_render?('README.apib')
   end
 
   def test_fails_gracefully_on_missing_commands

test/markups/README.apib

@@ -0,0 +1,12 @@
+# Example API
+This is an example Web API described in the [API Blueprint format](https://github.com/apiaryio/api-blueprint).
+
+## Message Resource [/message]
+An example resource.
+
+### Retrieve Message [GET]
+Retrieve the message.
+
++ Response 200 (text/plain)
+
+        Hello World!

test/markups/README.apib.html

@@ -0,0 +1,18 @@
+<h1>Example API</h1>
+
+<p>This is an example Web API described in the <a href="https://github.com/apiaryio/api-blueprint">API Blueprint format</a>.</p>
+
+<h2>Message Resource [/message]</h2>
+
+<p>An example resource.</p>
+
+<h3>Retrieve Message [GET]</h3>
+
+<p>Retrieve the message.</p>
+
+<ul>
+<li><p>Response 200 (text/plain)</p>
+
+<pre><code>Hello World!
+</code></pre></li>
+</ul>