Make interact example compatible with Python 3

Also cleared all output, because for now the notebook has to be run to
illustrate anything. And updated a couple of out of date names.
Fix infinite loop typo
Dockerfile to track the latest master
install direct dependencies, kernels
Instructions inside the Dockerfile
Submodule updating, comments
Try out setup.py submodule
Clone ipython/ipython directly
/srv/ was already created, just ensure its there
Create IPython profile with jupyter permissions
Workaround limitations in Docker Hub
Permissions everywhere
More workarounds
Switch back to ADD
Toss opinionated user creation out
Definitely don't want the direct submodule stuff
Update Dockerfile
use `git status` to check if it's a repo

not just checking if `.git` exists.

`.git` may be broken, or git may be unavailable.
use file://$PWD#egg=ipython[all] in Dockerfile

so we can install ipython[all] with pip.
Because .[all] doesn't work for whatever reason.
Removes need to install other dependencies with pip beforehand.
Merge pull request #6541 from takluyver/interact-examples-py3

Make interact example compatible with Python 3