Sam Williams

Add new method IPv4::isNetmask(). This provides functionality to test if an IPv4 address is a valid netmask.

This PR adds PHP-CS-Fixer as a dev dependency.

Using Namespaces

31

I am really liking this library, but perhaps we can embrace namespaces instead or require statements. It will make the code a lot cleaner. We can utilise the [PSR-0 standard](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md)...