Polish ansible settings: introduce separating lines
ansible-provision: Skip scala installation if installed already

Building scala is too time-expensive, so we might skip the task
if scala requirement is already satisfied.
Make provisioning faster: cache 'apt-get update' for a hour
Document how to do re-provisioning, make the process much verbose
Merge pull request #57 from wookayin/improve-ansible

ansible 설정 개선