Update YouTube embed post

Author: mmistakes

docs/_posts/2010-06-02-post-video-youtube.md

@@ -4,9 +4,25 @@ categories:
   - Post Formats
 tags:
   - Post Formats
-last_modified_at: 2017-03-09T12:58:20-05:00
+last_modified_at: 2017-03-23T15:33:37-04:00
 ---
 
-<iframe width="640" height="360" src="https://www.youtube-nocookie.com/embed/l2Of1-d5E5o?controls=0&amp;" frameborder="0" allowfullscreen></iframe>
+<div class="embed-responsive embed-responsive-16by9">
+  <iframe width="640" height="360" src="https://www.youtube-nocookie.com/embed/l2Of1-d5E5o?controls=0&amp;" frameborder="0" allowfullscreen></iframe>
+</div>
 
-This post test YouTube video embeds.
+This post tests YouTube video embeds.
+
+Simply wrap embeds with a `<div>` element and the appropriate classes:
+
+```html
+<!-- 16:9 aspect ratio -->
+<div class="embed-responsive embed-responsive-16by9">
+  <iframe class="embed-responsive-item" src="..."></iframe>
+</div>
+
+<!-- 4:3 aspect ratio -->
+<div class="embed-responsive embed-responsive-4by3">
+  <iframe class="embed-responsive-item" src="..."></iframe>
+</div>
+```