Change some collection functions(getNextEntity,getPrevEntity,getNextPage,getPreviousPage).  

#### getNextEntity

**Contents**

```javascript
//before
var hasNextElement = (this._iterator >= 0 && this._iterator <= this._list.length);
//after
var hasNextElement = (this._iterator >= 0 && this._iterator < this._list.length);
```

**Why**

If there is no next entity, false to return the modified

#### getPrevEntity

**Contents**

```javascript
//before
return this.list[this._iterator];
//after
return this._list[this._iterator];
```

**Why**

Wrong variable name

#### getNextPage & getPreviousPage

**Contents**

```javascript
//add code
} else {
	callback(true);
}
```

**why**

the return value is consistent