Add css-display-3.vim and test

See also: http://www.w3.org/TR/2014/WD-css-display-3-20140220/

test/test.html

@@ -118,6 +118,13 @@
         speak-as: auto;
       }
 
+      .display {
+        display-inside: block-level;
+        display-outside: inline-level;
+        display-extras: inline-list-item;
+        display-box: contents;
+      }
+
       .exclusions {
         wrap-flow: minimum;
         wrap-through: maximum;