chore(test-helper): setup promise polyfill for browser testing

relates to ReactiveX#998

Author: kwonoj

package.json

@@ -96,6 +96,7 @@
     "commitizen": "2.4.4",
     "coveralls": "2.11.4",
     "cz-conventional-changelog": "1.1.4",
+    "es6-promise": "^3.0.2",
     "esdoc": "0.4.3",
     "eslint": "1.5.1",
     "fs-extra": "0.24.0",

spec/helpers/test-helper.js

@@ -135,6 +135,13 @@ afterEach(function () {
   });
 
   global.__root__ = root;
+
+  //setup promise polyfill for browsers does not supports it
+  if (!(root.Promise || root.Rx && root.Rx.config && root.Rx.config.Promise)) {
+    Rx.config = {
+      Promise: require('es6-promise').Promise
+    };
+  }
 })();
 
 global.lowerCaseO = function lowerCaseO() {