This is an effort to automate testing Ubuntu packages inside temporary EC2
instances created on-demand. Not really there yet but it's a start.

First, copy settings.py.template to settings.py and fill it in with your AWS
credentials and other info. Then use it in your fabfile.py like this:

from fabric.api import *
from vm import *

def my_task()
    with temporary_ec2_instance(ami_id='ami-8cb33ebc'):
        sudo('apt-get install mypackage')

Specify the appropriate ami_id for the image you want (in the region you have
set in settings.py).

When this task is executed by Fabric, it will spin up a new instance, wait for
it to boot up, and then set env.host_string so that Fabric can connect to it.
You can only use this instance inside the 'with:' block, as when the block is
exited for any reason, the instance will be terminated. This keeps tests as
cheap as possible!