Docs: Add note about iOS 7.1 minimal-ui property

Ref: h5bp#1485.
Close: h5bp#1485.

Author: mcsheffrey

doc/extend.md

@@ -547,6 +547,13 @@ Home Screen icon. This works since iOS 6.
 <meta name="apple-mobile-web-app-title" content="">
 ```
 
+On iOS 7.1, you can minimize the top and bottom bars on the iPhone as the page
+loads, simply by adding the `minimal-ui` property to the `viewport` meta tag.
+
+```html
+<meta name="viewport" content="width=device-width, initial-scale=1, minimal-ui">
+```
+
 For further information please read the [official
 documentation](http://developer.apple.com/library/safari/#documentation/AppleApplications/Reference/SafariHTMLRef/Articles/MetaTags.html)
 on Apple's site.