Handling symbolic links #10

I found this library did not provide a way to deal with symbolic links, I am behind a fire wall here at work where I had to solve this so all I can do is put the changes for this in text, its a pretty small change,
if you add the properties 'version' and 'fileAttributes' as NSUInteger to FileInZipInfo and to the init method to set them and them fill them with the values unz_file_info.version and unz_file_info.external_fa you can then add the manually implemented property isSymbolicLink to FileInZipInfo like so

- (BOOL)isSymbolicLink {
    const NSUInteger ZipUNIXVersion = 3;
    const NSUInteger BSD_SFMT = 0170000;
    const NSUInteger BSD_IFLNK = 0120000;
    return (((self.version >> 8) == ZipUNIXVersion) && BSD_IFLNK == (BSD_SFMT & (self.fileAttributes >> 16)));
}

Alternatively you could just have a property isSymbolicLink and set it with the init method but I though that the version and fileAttributes maybe useful for other things. I also created an isDirectory property that just test the filename ends with '/', you may also need to test for '' as well if its a zip file created on windows.
I hope this is more help and hindrance.