Instead of hardcoding AZ, retrieve it from AWS

Docker-DCO-1.1-Signed-off-by: Aaron Feng aaron.feng@gmail.com (github: aaronfeng)
Support VPC and various improvements.

* Support VPC
* Lookup available AZ instead hardcode to us-east-1a.
* Lookup correct AMI id by name instead of hardcoded ami id.
* Change security_group name to security_group_id .
* Allow custom SSH port.

Docker-DCO-1.1-Signed-off-by: Aaron Feng aaron.feng@gmail.com (github: aaronfeng)
link to basic README

Docker-DCO-1.1-Signed-off-by: Aaron Feng aaron.feng@gmail.com (github: aaronfeng)
Merge pull request #119 from aaronfeng/retrieve-default-zone-from-aws

ec2 service: Support VPC and other fixes