Add Web Streams polyfill

package.json

@@ -83,7 +83,8 @@
     "node-fetch": "^2.1.2",
     "node-localstorage": "~1.3.0",
     "pako": "^1.0.6",
-    "rusha": "^0.8.12"
+    "rusha": "^0.8.12",
+    "web-streams-polyfill": "^1.3.2"
   },
   "repository": {
     "type": "git",

src/stream.js

@@ -1,5 +1,9 @@
 import util from './util';
 
+if (typeof ReadableStream === 'undefined') {
+  Object.assign(typeof window !== 'undefined' ? window : global, require('web-streams-polyfill'));
+}
+
 function concat(arrays) {
   const readers = arrays.map(getReader);
   let current = 0;

test/unittests.js

@@ -5,6 +5,9 @@ if (typeof Symbol === 'undefined') {
 if (typeof Promise === 'undefined') {
   require('core-js/fn/promise');
 }
+if (typeof ReadableStream === 'undefined') {
+  Object.assign(typeof window !== 'undefined' ? window : global, require('web-streams-polyfill'));
+}
 
 (typeof window !== 'undefined' ? window : global).resolves = function(val) {
   return new Promise(function(res) { res(val); });