Revert "Update Webpack + deps, remove now unnecessary polyfills" (#2479)

* Revert "Update Webpack + deps, remove now unnecessary polyfills (#2410)"

This reverts commit 189b34c45a.

* Fix build (#2496)

* Change syntax to see if build passes

* Test commit

* Test with node 10

* Test adding all browsers in travis

* remove other browsers when running on travis

lib/helpers/buildURL.js

@@ -39,7 +39,7 @@ module.exports = function buildURL(url, params, paramsSerializer) {
         return;
       }
 
-      if (Array.isArray(val)) {
+      if (utils.isArray(val)) {
         key = key + '[]';
       } else {
         val = [val];

lib/helpers/parseHeaders.js

@@ -34,8 +34,8 @@ module.exports = function parseHeaders(headers) {
 
   utils.forEach(headers.split('\n'), function parser(line) {
     i = line.indexOf(':');
-    key = line.substr(0, i).trim().toLowerCase();
-    val = line.substr(i + 1).trim();
+    key = utils.trim(line.substr(0, i)).toLowerCase();
+    val = utils.trim(line.substr(i + 1));
 
     if (key) {
       if (parsed[key] && ignoreDuplicateOf.indexOf(key) >= 0) {