Arcanist linter configuration
This configuration forks the configuration I wrote for rNOTIF.
It allows to use minimal lint check (spelling, JSON, php -l).
To use phpcs isn't really useful here, as WP-CLI conventions
don't follow PSR-1.
Test Plan: arc lint --everything
Maniphest Tasks: T887
Differential Revision: http://devcentral.nasqueron.org/D437