Remove unused arrays.pluck function

lib/utils/arrays.js

@@ -54,10 +54,6 @@ var arrays = {
 
   contains: function(array, valueOrPredicate) {
     return arrays.indexOf(array, valueOrPredicate) !== -1;
-  },
-
-  pluck: function(array, key) {
-    return array.map(function (e) { return e[key]; });
   }
 };