updated README.md

README.md

 # WeixinAuthorize
 
+Support using [Redis](http://redis.io) to store `access_token`
+
 ## Installation
 
 Add this line to your application's Gemfile:
@@ -27,27 +29,19 @@ Or install it yourself as:
 $client ||= WeixinAuthorize::Client.new(ENV["APPID"], ENV["APPSECRET"])
 ```
 
-If you use [Redis](http://redis.io) to store your access_token, you can also specify the `key`:
-
-```ruby
-$client ||= WeixinAuthorize::Client.new(ENV["APPID"], ENV["APPSECRET"], "your_store_key")
-```
+## Option: use [Redis](http://redis.io) to store your access_token (Recommend)
 
-## Configure to use Redis to store your access_token (Recommend)
+  **If you don't use Redis, it will send a request to get a new access_token everytime!**
 
 * Create file in: `config/initializers/weixin_authorize.rb`
 
   ```ruby
 
-    require "redis"
-    require "redis-namespace"
-    require "weixin_authorize"
-
   # don't forget change namespace
-    namespace = "your_app_name_weixin:weixin_authorize"
-    redis = Redis.new(:host => "127.0.0.1",:port => "6379", :db => 15)
+  namespace = "app_name_weixin:weixin_authorize"
+  redis = Redis.new(:host => "127.0.0.1", :port => "6379", :db => 15)
 
-    # Delete the current namespace keys when restart everytime.
+  # cleanup keys in the current namespace when restart server everytime.
   exist_keys = redis.keys("#{namespace}:*")
   exist_keys.each{|key|redis.del(key)}
 
@@ -57,7 +51,16 @@ $client ||= WeixinAuthorize::Client.new(ENV["APPID"], ENV["APPSECRET"], "your_st
   WeixinAuthorize.configure do |config|
     config.redis = redis
   end
+
+  ```
+
+* You can also specify the `key`, but it is optionly.
+
+  ```ruby
+
+  $client ||= WeixinAuthorize::Client.new(ENV["APPID"], ENV["APPSECRET"], "your_store_key")
   ```
+  **Note: ** `your_store_key` should be unique for every account!
 
 ### 获取用户管理信息