`default-directoy` can be "~/" and needs expansion.
`(cabbage-project-p)` checks if a project is found.
`(cabbage-project-expand-path)` builds relative project paths.
Merge pull request #184 from senny/project_api_improvements

Improved project API
add dynamic phpunit command building
Merge pull request #183 from tonini/php-mode-handle-phpunit-config

add dynamic phpunit command building