Integrate PHP Code Sniffer with VIP Scanner using the WordPress Coding Standards

The test requires that the [WordPress Coding Standards](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards) be installed. Please see that page for more information. If the coding standards or PHPCS are not installed, a warning is outputted.

The code for this lives within a new `WordPressCodingStandardsCheck`. This check has been added to the `WP.com Theme Review` and the `VIP Theme Review`.

Issues raised by this check follow the following scheme:
- `Blockers`: Most likely a severe security or performance concern.
- `Warnings`: Most likely a performance or other concern.
- `Notes`: Stylistic issues or other issues that do not effect security or performance.

For a sample output of the `VIP Theme Check` run on `TwentyFourteen` see: https://gist.github.com/Mobius5150/8483591

Note that the `WordPressCodingStandardsCheck` does run fairly slowly due to PHP Code Sniffer and only scans the .php and .css files.