add MixItUp

Author: Nitrino

README.md

@@ -924,6 +924,7 @@
     + [Shapeshift](https://github.com/McPants/jquery.shapeshift) is a plugin which will dynamically arrange a collection of elements into a column grid system similar to Pinterest.
     + [CollagePlus](http://ed-lea.github.io/jquery-collagePlus/): This plugin for jQuery will arrange your images to fit exactly within a container.
     + [Masonry](http://masonry.desandro.com/)  JavaScript Cascading grid layout library
+    + [MixItUp](https://mixitup.kunkalabs.com/) jQuery plugin providing animated filtering and sorting.
 + Jobs & Hiring
     + [GitHub Jobs](https://jobs.github.com/)
     + [Authentic Jobs](http://www.authenticjobs.com/)