Update documentation

Author: JacksonTian

lib/api_common.js

@@ -32,6 +32,10 @@ AccessToken.prototype.isValid = function () {
  * 1. 调用用户传入的获取token的异步方法，获得token之后使用
  * 2. 使用appid/appsecret获取token。并调用用户传入的保存token方法保存
  *
+ * Tips:
+ *
+ * - 如果跨机器运行wechat模块，需要注意同步机器之间的系统时间。
+ *
  * Examples:
  * ```
  * var API = require('wechat').API;

lib/oauth.js

@@ -107,11 +107,13 @@ OAuth.prototype.getAuthorizeURL = function (redirect, state, scope) {
  * Result:
  * ```
  * {
- *  "access_token": "ACCESS_TOKEN",
- *  "expires_in": 7200,
- *  "refresh_token": "REFRESH_TOKEN",
- *  "openid": "OPENID",
- *  "scope": "SCOPE"
+ *  data: {
+ *    "access_token": "ACCESS_TOKEN",
+ *    "expires_in": 7200,
+ *    "refresh_token": "REFRESH_TOKEN",
+ *    "openid": "OPENID",
+ *    "scope": "SCOPE"
+ *  }
  * }
  * ```
  * @param {String} code 授权获取到的code
@@ -146,11 +148,13 @@ OAuth.prototype.getAccessToken = function (code, callback) {
  * Result:
  * ```
  * {
- *  "access_token": "ACCESS_TOKEN",
- *  "expires_in": 7200,
- *  "refresh_token": "REFRESH_TOKEN",
- *  "openid": "OPENID",
- *  "scope": "SCOPE"
+ *  data: {
+ *    "access_token": "ACCESS_TOKEN",
+ *    "expires_in": 7200,
+ *    "refresh_token": "REFRESH_TOKEN",
+ *    "openid": "OPENID",
+ *    "scope": "SCOPE"
+ *  }
  * }
  * ```
  * @param {Function} callback 回调函数