ENH: Udpated cli for doto

Ben, this is to help with binstar build

Check out the deploy script that this enables me to write:
```sh
set -e
DROPLET=$1
FAB_COMMAND=$2
IMAGE_NAME=$3

if [ -z "$DROPLET" ]; then
    echo "Positional argument 0 (DROPLET) must be given"
    exit 1
fi

if [ -z "$FAB_COMMAND" ]; then
    echo "Positional argument 1 (FAB_COMMAND) must be given"
    exit 1
fi

if [ -z "$IMAGE_NAME" ]; then
    echo "Positional argument 2 (IMAGE_NAME) must be given"
    exit 1
fi


set -x

doto image -a destroy $IMAGE_NAME

IP_ADDR=$(doto info $DROPLET ip_address)
doto --wait power-off $DROPLET
doto --wait rebuild $DROPLET

fab -i ~/.ssh/binstar-build.pem -H $IP_ADDR -u root create_binstar_user
fab -i ~/.ssh/binstar-build.pem -H $IP_ADDR -u binstar $FAB_COMMAND

doto --wait power-off $DROPLET
doto --wait snapshot $DROPLET $IMAGE_NAME
set +x
```