Include PHPCS path in `$PATH`. Install WP standards for PHPCS.

Before:

```bash
/srv/www/phpcs/scripts/phpcs --standard=CodeSniffer/Standards/WordPress/WordPress/ruleset.xml ./htdocs/wp-load.php
```

After:
```bash
phpcs --standard=WordPress ./htdocs/wp-load.php
```
Well, OK then. That works. :dancer: 

```
vagrant@vvv:/srv/www/glow-blogs$ phpcs --config-set installed_paths ./CodeSniffer/Standards/WordPress/
vagrant@vvv:/srv/www/glow-blogs$ phpcs -i
The installed coding standards are MySource, PEAR, PHPCS, PSR1, PSR2, Squiz, Zend, WordPress, WordPress-Core, WordPress-Extra and WordPress-VIP
```