add cache module

cache/README.md

@@ -0,0 +1,52 @@
+## cache
+cache is a golang cache manager. It can use cache for many adapters. The repo is inspired by `database/sql` .
+
+##How to install
+
+	go get github.com/astaxie/beego/cache
+
+	
+##how many adapter support
+
+Now this cache support memory/redis/memcache	
+	
+## how to use it
+first you must import it
+
+
+	import (
+		"github.com/astaxie/beego/cache"
+	)
+
+then init an Cache(memory adapter)
+
+	bm, err := NewCache("memory", `{"interval":60}`)	
+
+use it like this:	
+	
+	bm.Put("astaxie", 1, 10)
+	bm.Get("astaxie")
+	bm.IsExist("astaxie")
+	bm.Delete("astaxie")
+	
+## memory adapter
+memory adapter config like this:
+
+	{"interval":60}
+
+interval means the gc time. The cache will every interval time to check wheather have item expired.	
+
+## memcache adapter
+memory adapter use the vitess's [memcache](code.google.com/p/vitess/go/memcache) client.
+
+the config like this:
+
+	{"conn":"127.0.0.1:11211"}
+
+
+## redis	 adapter
+redis adapter use the [redigo](github.com/garyburd/redigo/redis) client.
+
+the config like this:
+
+	{"conn":":6039"}