Install libsodium for privatebin

src/freedombone-app-privatebin

 
     apt-get -yq install php-gettext php-curl php-gd php-mysql git curl
     apt-get -yq install memcached php-memcached php-intl exiftool libfcgi0ldbl
+    apt-get -yq install php-libsodium libsodium18
 
     if [ ! -d /var/www/$PRIVATEBIN_DOMAIN_NAME ]; then
         mkdir /var/www/$PRIVATEBIN_DOMAIN_NAME