The requirements.txt file isn't correct

We now depend on jinja2 and docker-py for building images.

We no longer depend on docker-compose for any part of our
runtime so removing it as a requirement.  If we keep compose
in the tree, it will be for reference only, not for runtime.

Change-Id: Ie663a0f183e74c14f01e9cb4fdc8763355c6415a
Partially-Implements: blueprint dockerfile-template