Reports/Summary: sort files based on directory
Reports/Summary: sort files based on directory

The original sort order of the file names in the summary report was alphabetic and did not take subdirectories into account.

This could result in a list like:
```
dir/afile/subdir/file.php
dir/afile.php
dir/b/subdir/file.php
dir/cfile.php
```

The change proposed in this PR sorts the file names in a way that the directory layout is taken into account, so the above list would now display as:
```
dir/afile.php
dir/cfile.php
dir/afile/subdir/file.php
dir/b/subdir/file.php
```

stronk7/PHP_CodeSniffer,jrfnl/PHP_CodeSniffer,squizlabs/PHP_CodeSniffer,stronk7/PHP_CodeSniffer,squizlabs/PHP_CodeSniffer,jrfnl/PHP_CodeSniffer,jrfnl/PHP_CodeSniffer,squizlabs/PHP_CodeSniffer,stronk7/PHP_CodeSniffer