Add the availibility zone to the knife ec2 server listing.

When deploying a multi-zone scalable architecture
knowing what zones your servers are currently in
is necessary.

Know when knife ec2 server list is ran, the zone is displayed after the
Private IP.
Eg:
    Instance ID  Public IP           Private IP            Zone            Flavor        Image         SSH Key        Security Groups      State  
    i-a999f9cc   107.22.247.27  10.204.215.104  us-east-1a  m1.small  ami-29f41830  administrator  production          running

I also bumped the minor version to 16.