Replace es6-promisify with simple polyfill

referto: reactnativecn#37

Author: sunkibaek

Diff for: index.js

@@ -3,10 +3,17 @@
  */
 
 import {NativeModules, NativeAppEventEmitter} from 'react-native';
-import promisify from 'es6-promisify';
 
 const {WeiboAPI} = NativeModules;
 
+function promisify(fn, handler) {
+    return function (...args) {
+        return new Promise(function (resolve, reject) {
+            fn(...args, handler.bind({ resolve, reject }))
+        })
+    }
+}
+
 // Used only with promisify. Transform callback to promise result.
 function translateError(err, result) {
     if (!err) {

Diff for: package.json

@@ -24,8 +24,5 @@
   "bugs": {
     "url": "https://github.com/reactnativecn/react-native-weibo/issues"
   },
-  "homepage": "https://github.com/reactnativecn/react-native-weibo#readme",
-  "dependencies": {
-    "es6-promisify": "^3.0.0"
-  }
+  "homepage": "https://github.com/reactnativecn/react-native-weibo#readme"
 }