Building image

Since you can't download packer from curl (403 forbidden), had to download it manually and copy it into the image.

docker run -ti -v ~/Downloads:/app ubuntu:15.04 /bin/bash
# then copy Downloads/packer into /usr/local/packer
# then exit and:
docker commit CONTAINER_ID treeder/packer:0.8.1
docker push treeder/packer

Using image

dj run treeder/packer:0.8.1 /usr/local/packer/packer