Fix import error with cloud_init task
Fixes #14 and #78
S3 images can now be bootstrapped outside EC2.
However, this fix adds the requirement of a "region" setting.
At some point we could make "region" optional and fail when bootstrap-vz
is run outside EC2 and no "region" is set.
Require hostname setting for vagrant plugin
Also, fix reference to vbox src to a revision
Simplify adding tasks
There is now a get_standard_groups function
Add ssh_group, which configures SSH properly
Remove unused imports
Create security group (part of standard group)
Don't add initd installation task in vbox provider
Add get_standard_rollback_tasks()
This simplifies the the providser rollback_tasks fn considerably
Generalize "grub only on partitioned volumes" err
(move it into base manifest validation)