removed default phpcs standard

The default phpcs standard of ```--standard=PHPCS``` doesn't make sense to me. I can set the global standard with 

    phpcs --config-set default_standard PSR2

but phpqa's default *overrides* my default standard. So I *have* to re-specify my default standard again in .vimrc. Why not just default to the phpcs default standard and let people add a specific standard if they like?