implement util.splitList() with slice() instead of splice()

lib/util.js

@@ -50,13 +50,9 @@ class Util {
    * Splits a list into a list of lists each with maximum length LIMIT
    */
   static splitList(list, limit) {
-    if (list.length <= limit)
-      return [list]
-
     const lists = []
-    while (list.length) {
-      lists.push(list.splice(0, limit))
-    }
+    for (let i=0; i < list.length; i += limit)
+      lists.push(list.slice(i, i+limit))
     return lists
   }