demos : use modulus for randomish size classes

_includes/random-sizes.js

@@ -1,10 +1,12 @@
 
-      // hacky way of adding random size classes
+      // add randomish size classes
       $container.find('.element').each(function(){
-        if ( Math.random() > 0.6 ) {
-          $(this).addClass('width2');
+        var $this = $(this),
+            number = parseInt( $this.find('.number').text(), 10 );
+        if ( number % 7 % 2 === 1 ) {
+          $this.addClass('width2');
         }
-        if ( Math.random() > 0.6 ) {
-          $(this).addClass('height2');
+        if ( number % 3 === 0 ) {
+          $this.addClass('height2');
         }
       });