function AsyncZipDeflate(filename, opts) {
        var _this = this;
        if (!opts)
            opts = {};
        ZipPassThrough.call(this, filename);
        this.d = new AsyncDeflate(opts, function (err, dat, final) {
            _this.ondata(err, dat, final);
        });
        this.compression = 8;
        this.flag = dbf(opts.level);
        this.terminate = this.d.terminate;
    }
Creates an asynchronous DEFLATE stream that can be added to ZIP archives
@param filename The filename to associate with this data stream
@param opts The compression options