Support the new VIP coding standards project

[MattGeri]

WP Dev Lib currently supports the outdated WordPress-VIP coding standards ruleset that will no longer be supported as of WPCS 2.0.0. Currently, when we pull the WPCS project, we checkout the develop branch which is the beta of 2.0.0 and thus, builds fail when trying to use the WordPress-VIP rules.

The solution is to incorporate https://github.com/Automattic/VIP-Coding-Standards/, but a decision needs to be made on how to include those rules. Should we always install them? Should we selectively include them based on the specified rules of the current project? That would be the most obvious, but is more complex as we would need to parse the rules file in the check-diff.sh script.

[westonruter]

If VIP-Coding-Standards is installed with composer along with WPCS and PHPCS, then it should all work fine as it is today. The AMP plugin is using PHPCompatibility even though wp-dev-lib doesn't know anything about it specifically:

https://github.com/ampproject/amp-wp/blob/c92e129333a8518088a37d47594079b537121d70/phpcs.xml#L35-L39

I think it's best to install all dependencies via composer so that the project can be more specific about its environment.

[kasparsd]

@MattGeri As a temporary fix you can override the WPCS version in .dev-lib like so:

WPCS_GIT_TREE=master

See this section of the readme.

[kasparsd]

Would be nice to add VIP-Coding-Standards to the suggested packages list.