Check if expand is used to define files

When we use a globbling pattern with expand to define all sources, el.dest in filerev task contains the basename too.

Example with this conf :
```
filerev: {
  files: {
    expand: true,
    cwd: 'test/fixtures',
    src: ['*.png'], // ex. file.png
    dest: 'test/tmp/expand'
 }
}
```

```
Destination dir test/tmp/expand/another.png does not exists for target withExpand: creating
✔ test/fixtures/another.png changed to another.d9170849.png
Destination dir test/tmp/expand/cfgfile.png does not exists for target withExpand: creating
✔ test/fixtures/cfgfile.png changed to cfgfile.a0539763.png
Destination dir test/tmp/expand/file.png does not exists for target withExpand: creating
✔ test/fixtures/file.png changed to file.a0539763.png
```

Finally filerev copy ```test/fixtures/another.png``` to ```test/tmp/expand/another.png/another.d9170849.png```

I had a test and a fix proposal to change this behaviour.