ELocker实现 Closeable接口，支持jdk7 try-with-resources 语句
example:
```java
public static void main(String[] args){
String key = "key";
try (ELocker locker = locker(key, 100)){
for (int i = 0; i < 10; i++) {
System.out.println(Thread.currentThread().getId() + ">>" + i);
Thread.sleep(100l);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
```
