Bugfix/docker image upgrade

[ghost]

Description

Docker image (re-)build improvements and complete requirements upgrade.

Dependency upgrade created using the following inside the new base image:

sed -E 's/==.*//' /app/requirements.txt | while read pypkg; do
    pip install --upgrade "$pypkg" 2>&1 | sed -n -E 's/^.*Downloading ([^-]+)-(.*)(-py.*\.whl|\.tar).*/\1==\2/p'
done

Testing

docker build -t mozilla/tokenserver:local .
docker run --rm mozilla/tokenserver:local test_all

Issue(s)

Closes #215
Closes #190
Supersedes #212