I know this not the first vim plugin available to update a DNS-zone serial number. Here is a few reasons why I chose not to use the canonical one:
* there is no license and therefore it is not free;
* it is unmaintained;
* it is bugged;
* it lacks functionalities.
It chose not to fork the original plugin but to write a new one from scratch mainly for legal purposes, but also because I did not found the code as simple as I expected.
By default, each time you save a `bindzone` file, the script will look for the DNS serial number and update it. You can also update it without saving the file by invoking the `:DNSSerialUpdate` function.