Add function percentage

lib/less/functions.js

@@ -167,6 +167,9 @@ tree.functions = {
     argb: function (color) {
         return new(tree.Anonymous)(color.toARGB());
 
+    },
+    percentage: function(n) {
+        return new(tree.Dimension)(n.value * 100, '%');
     }
 };
 

test/css/functions.css

@@ -24,6 +24,7 @@
   lightness: 95%;
   rounded: 11;
   roundedpx: 3px;
+  percentage: 20%;
 }
 #alpha {
   alpha: rgba(153, 94, 51, 0.6);

test/less/functions.less

@@ -28,6 +28,7 @@
   lightness: lightness(hsl(98, 12%, 95%));
   rounded: round(@r/3);
   roundedpx: round(10px / 3);
+  percentage: percentage(10px / 50);
 }
 
 #alpha {