Always mention which file has the problem

Here we see the filename is mentioned when multiple files are given,
```
$ exif c.jpg a.jpg b.jpg 
'c.jpg' is not readable or does not contain EXIF data!
```
But here we don't,
```
$ exif a.jpg b.jpg c.jpg
Corrupt data
The data provided does not follow the specification.
ExifLoader: The data supplied does not seem to contain EXIF data.
```
$ exif --version
0.6.22
