refactor(*): utilize es6 spread in addWords/removeWords

BREAKING CHANGE: changes the way addWords is used, no longer accepts a single array as a parameter unless used with the spread operator

lib/badwords.js

@@ -79,7 +79,8 @@ var Filter = (function () {
    */
   Filter.prototype.addWords = function addWords() {
     let words = Array.from(arguments);
-    this.list = this.list.concat(words);
+
+    this.list.push(...words);
 
     words.forEach(function (word) {
       if (!!~this.exclude.indexOf(word)) {
@@ -93,8 +94,7 @@ var Filter = (function () {
    * @param {(string|string[])} word - Word to add to whitelist.
    */
   Filter.prototype.removeWords = function removeWords() {
-    let words = Array.from(arguments);
-    this.exclude.push.apply(this.exclude, words);
+    this.exclude.push(...Array.from(arguments));
   };
 
   return Filter;