fix load balancer creation
fix repo push/clone
wip: private subnet support

Issue #14

Work-in-progress

- Launch instances in private subnet, while load balancers are in
public subnet.
- Connect to instances in private subnet through a bastion machine
(TODO auto-create bastion machine).
- VPC also must already be configured (TODO auto-configure VPC).
- Currently forces this behavior (TODO should be optional).