Add Memcached SASL Connection Support

[guodong000]

Add SASL connection support

using

// using SASL
org.mybatis.caches.memcached.sasl=true
// SASL uername
org.mybatis.caches.memcached.username=${username}
// SASL password
org.mybatis.caches.memcached.password=${password}

Reference: https://code.google.com/p/spymemcached/wiki/Examples

[guodong000]

My English is not good. Please forgive me. ^_^

[liyiorg]

给力，可惜作者忘记这事了。阿里云的缓存是需要密码访问的！google 的 wiki 示例无法访问。

[guodong000]

Google那个是spymemcached的一个Example，需要翻墙的。。。
我就是因为需要使用阿里云的缓存，所以才自己做的适配，说粗来都是泪啊。。。。

[hazendaz]

@guodong000 if you can rebase this, I'll accept it. It looks primarily like extra functionality that would otherwise not harm anything so I'm pretty open to bringing this into the main code.