Axios ES2017 (#4787)

* Added AxiosHeaders class;

* Fixed README.md href;

* Fixed a potential bug with headers normalization;

* Fixed a potential bug with headers normalization;
Refactored accessor building routine;
Refactored default transforms;
Removed `normalizeHeaderName` helper;

* Added `Content-Length` accessor;
Added missed `has` accessor to TS types;

* Added `AxiosTransformStream` class;
Added progress capturing ability for node.js environment;
Added `maxRate` option to limit the data rate in node.js environment;
Refactored event handled by `onUploadProgress` && `onDownloadProgress` listeners in browser environment;
Added progress & data rate tests for the http adapter;
Added response stream aborting test;
Added a manual progress capture test for the browser;
Updated TS types;
Added TS tests;
Refactored request abort logic for the http adapter;
Added ability to abort the response stream;

* Remove `stream/promises` & `timers/promises` modules usage in tests;

* Use `abortcontroller-polyfill`;

* Fixed AxiosTransformStream dead-lock in legacy node versions;
Fixed CancelError emitting in streams;

* Reworked AxiosTransformStream internal logic to optimize memory consumption;
Added throwing an error if the request stream was silently destroying (without error) Refers to #3966;

* Treat the destruction of the request stream as a cancellation of the request;
Fixed tests;

* Emit `progress` event in the next tick;

* Initial refactoring;

* Refactored Mocha tests to use ESM;

* Refactored Karma tests to use rollup preprocessor & ESM;
Replaced grunt with gulp;
Improved dev scripts;
Added Babel for rollup build;

* Added default commonjs package export for Node build;
Added automatic contributors list generator for package.json;

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/helpers/parseHeaders.js

@@ -1,15 +1,15 @@
 'use strict';
 
-var utils = require('./../utils');
+import utils from './../utils.js';
 
-// Headers whose duplicates are ignored by node
+// RawAxiosHeaders whose duplicates are ignored by node
 // c.f. https://nodejs.org/api/http.html#http_message_headers
-var ignoreDuplicateOf = [
+const ignoreDuplicateOf = utils.toObjectSet([
   'age', 'authorization', 'content-length', 'content-type', 'etag',
   'expires', 'from', 'host', 'if-modified-since', 'if-unmodified-since',
   'last-modified', 'location', 'max-forwards', 'proxy-authorization',
   'referer', 'retry-after', 'user-agent'
-];
+]);
 
 /**
  * Parse headers into an object
@@ -21,32 +21,33 @@ var ignoreDuplicateOf = [
  * Transfer-Encoding: chunked
  * ```
  *
- * @param {String} headers Headers needing to be parsed
+ * @param {String} rawHeaders Headers needing to be parsed
  *
  * @returns {Object} Headers parsed into an object
  */
-module.exports = function parseHeaders(headers) {
-  var parsed = {};
-  var key;
-  var val;
-  var i;
+export default rawHeaders => {
+  const parsed = {};
+  let key;
+  let val;
+  let i;
 
-  if (!headers) { return parsed; }
-
-  utils.forEach(headers.split('\n'), function parser(line) {
+  rawHeaders && rawHeaders.split('\n').forEach(function parser(line) {
     i = line.indexOf(':');
-    key = utils.trim(line.slice(0, i)).toLowerCase();
-    val = utils.trim(line.slice(i + 1));
+    key = line.substring(0, i).trim().toLowerCase();
+    val = line.substring(i + 1).trim();
 
-    if (key) {
-      if (parsed[key] && ignoreDuplicateOf.indexOf(key) >= 0) {
-        return;
-      }
-      if (key === 'set-cookie') {
-        parsed[key] = (parsed[key] ? parsed[key] : []).concat([val]);
+    if (!key || (parsed[key] && ignoreDuplicateOf[key])) {
+      return;
+    }
+
+    if (key === 'set-cookie') {
+      if (parsed[key]) {
+        parsed[key].push(val);
       } else {
-        parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
+        parsed[key] = [val];
       }
+    } else {
+      parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
     }
   });