update the way to check if the window.localStorage supported or not 

I'm just thinking that we don't need the hasLocalStorage(), since it's easy to know if the window.localStorage supported or not by following code

```javascript
if(window.localStorage){
...//it's supported by current browser

}
```
since we already get the reference of window.localStorage by  `Backbone.localStorage()`
so just added following and remove the code added by @remmons

```javascript
if(this.localStorage()){

}
```