The UID of created user should be set to the UID of the user that will
be running the image/container to set appropriate permissions on files
within notebooks directory. Default 1000 should be ok for users using
the default account created while installing linux.
- rearranged a Dockerfile to allow for incremental build
- switched running from root to "default new user"
- added the (easy to opt-out) configuration to use blank password
- added python-graphviz which enables DT visualization in notebooks
- added nbdime for "sensible notebook comparison"
- added custom command to "nbdiff" a notebook with its checkpointed version
- added simple README.md
ziembla