update base64-js version. follow up #6961

Summary:
**Motivation**
This is originally a follow up of PR #6327 by dewe and jeremyong
And mkonicek indicated this should split into a separate PR.

Now philikon takes over #6327 as #6961

**Test Plan:**
According to #6961 and #6889
Load WebSocketExample in UIExplorer app and start websocket test server script and test sending binary data on both iOS and Android
Closes https://github.com/facebook/react-native/pull/6937

Reviewed By: javache

Differential Revision: D3669596

Pulled By: mkonicek

fbshipit-source-id: 342e29eb34de882bcbd9f297aab71dd6bb236748

package.json

@@ -149,7 +149,7 @@
     "babel-register": "^6.6.0",
     "babel-types": "^6.6.4",
     "babylon": "^6.8.2",
-    "base64-js": "^0.0.8",
+    "base64-js": "^1.1.2",
     "bser": "^1.0.2",
     "chalk": "^1.1.1",
     "commander": "^2.9.0",