SASL with Memcached is only supported with binary protocol

I saw warning messages when I used MamchedEngine for Session Handler(use MemCachier).
Memcached::setSaslAuthData() required binary protocol.

```
Warning (2): Memcached::setSaslAuthData(): SASL is only supported with binary protocol [CORE/Cake/Cache/Engine/MemcachedEngine.php, line 130]

Memcached::setSaslAuthData() - [internal], line ??
MemcachedEngine::init() - CORE/Cake/Cache/Engine/MemcachedEngine.php, line 130
Cache::_buildEngine() - CORE/Cake/Cache/Cache.php, line 180
Cache::config() - CORE/Cake/Cache/Cache.php, line 151
Configure::{closure}() - ROOT/Config/bootstrap/environments/heroku.php, line 43
Environment::setup() - ROOT/Plugin/Environments/Lib/Environment.php, line 101
Environment::start() - ROOT/Plugin/Environments/Lib/Environment.php, line 45
include - ROOT/Config/bootstrap/environments.php, line 8
include - ROOT/Config/bootstrap.php, line 19
Configure::bootstrap() - CORE/Cake/Core/Configure.php, line 92
include - CORE/Cake/bootstrap.php, line 175
[main] - ROOT/webroot/index.php, line 85
```

This PR is added binary protocol option in MemcachedEngine.