Fix the `report` option

Fix the `report` option by using  `grunt.log` instead of  `grunt.verbose`

I upgraded from `0.2.x` and there `uglify` had one `grunt.log` print:
```
File dist/1/xhook.min.js created: 13.23 kB → 5.82 kB → 2.52 kB (gzip)
```

It seems to only `grunt.verbose` print now. Maybe this was on purpose?