Change ibuffer binding to ibuffer-other-window

```
(global-set-key (kbd "C-x C-b") 'ibuffer)
```

The default behavior is closer to 
```
(global-set-key (kbd "C-x C-b") 'ibuffer-other-window)
```

Isn't it? Would it make sense to reflect the default behavior as closely as possible with the improved tool?