utils.hpp length check

[RPGillespie6]

utils.hpp contains the following length check for is_compressed:

return size > 2 && ...

However, it only uses the first two bytes. I would vote that length check should be return size >= 2 && ...

This would allow me to do something like:

        char gzipHeader[2];
        file.read(gzipHeader, 2);
        file.seekg(0, ios::beg); // rewind

        if (gzip::is_compressed(gzipHeader, 2))
            // do something...