Fix phpcs failing

All Travis builds are currently failing because of a new WP Coding standards release. The new version has split the repo into four repos, one main and three with specific subset rules for different purposes.
The new release also contains numerous updates/improved sniffs.

This pull request deals with:
1. fixing newly detected code style errors
2. updated phpcs config file based on which the current (master) codebase will pass
3. updated travis file to also download the relevant second WPCS repo