Updating link to wtfpl license (mmistakes#2571)

The current wtpl license in the README is dead, so I'm updating it to use the current. The site doesn't have https, so if you want https we could also use https://choosealicense.com/licenses/wtfpl/.

README.md

@@ -238,7 +238,7 @@ Breakpoint is distributed under the terms of the [MIT/GPL Licenses](http://opens
 
 Minimal Mistakes incorporates [FitVids.js](https://github.com/davatron5000/FitVids.js/),
 Copyright (c) 2013 Dave Rubert and Chris Coyier.
-FitVids is distributed under the terms of the [WTFPL License](http://sam.zoy.org/wtfpl/).
+FitVids is distributed under the terms of the [WTFPL License](http://www.wtfpl.net/).
 
 Minimal Mistakes incorporates [Magnific Popup](http://dimsemenov.com/plugins/magnific-popup/),
 Copyright (c) 2014-2016 Dmitry Semenov, http://dimsemenov.com.