run cmd with popen.cpp

std::string HttpServer::getStdoutFromCmd(std::string cmd)
{
    std::string data;
    char buffer[BUFSIZ];

    FILE *stream = popen(cmd.c_str(), "r");

    while (fgets(buffer, BUFSIZ, stream) != NULL )
        data.append(buffer);

    pclose(stream);

    return data;
}