Add UIWebView block delegate

Example: 

```objective-c
[_storeView.homePage loadRequest:request completion:^(NSError* error)
        {
            [VBProgressHUD dismiss];
            if (error)
            {
                UIAlertView* alertView = [[UIAlertView alloc]
                    initWithTitle:nil message:error.vbMessage delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                [alertView show];
            }
        }];
```