Documentation might be outdated for -v

The manual says `-v` takes a number:

https://github.com/containers/krunvm/blob/v0.2.3/docs/krunvm.1.txt#L39-L40

```
*-v* _NUM_::
  Sets the verbosity level, from the lowest (0) to the highest (5).
```

but trying `-v 5` results in:

```
error: Found argument '5' which wasn't expected, or isn't valid in this context
```
