use cron resource provided by cron cookbook to set up cron
Merge remote-tracking branch 'inviqa/develop' into feature/use-cron-cookbook-for-crontab

Conflicts:
	metadata.rb
	recipes/crontab.rb
Merge pull request #70 from mlopes/feature/use-cron-cookbook-for-crontab

Feature/use cron cookbook for crontab