Adds ability to specifie user/group for install files

Signed-off-by: Christophe Courtaut <christophe.courtaut@gmail.com>
Uses tar cookbook instead of command to extract WP

Signed-off-by: Christophe Courtaut <christophe.courtaut@gmail.com>
Merge pull request #30 from kri5/master

Ability to use specific user/group for wordpress install files