Updates to requirements.txt.

- Replace docker-py with docker. docker-py is deprecated and from what I
can gather no Ansible module currently requires it (unless you're still
on Python 2.6). It also conflicted with the docker package required by
other packages (like docker-compose) and would make for interesting
errors.
- Add hashin, yet another package update utility.
- Add cookicutter, used it before.

requirements.txt

@@ -7,13 +7,15 @@ bcrypt
 black
 boto
 boto3
+cookiecutter
 cryptography
 dnspython
+docker
 docker-compose
-docker-py
 flit
 Glances
 gunicorn
+hashin
 httpbin
 httpie
 identify