Correcting Mimetype regexp

Newer PHP versions uses "-" as a range selector onto expression, not as a character, causing compilation error

```
Compilation failed: invalid range in character class at offset 7
```

| Mime | Validation |
| --- | --- |
| image/vnd.djvu | http://rubular.com/r/fBWs9cQJgc |
| text/x-jquery-tmpl | http://rubular.com/r/d3X3XawW4Q |
| application/vnd.debian.binary-package | http://rubular.com/r/uaIUP8q557 |