Convert readthedocs links for their .org -> .io migration for hosted projects

As per [their blog post of the 27th April](https://blog.readthedocs.com/securing-subdomains/) ‘Securing subdomains’:

> Starting today, Read the Docs will start hosting projects from subdomains on the domain readthedocs.io, instead of on readthedocs.org. This change addresses some security concerns around site cookies while hosting user generated data on the same domain as our dashboard.

Test Plan: Manually visited all the links I’ve modified.

use cdn for apt

Build matplotlib font cache during docker build.

httpredir fails semi-regularly

Update ipywidgets to 5.2

Workaround for R plotting regression

Pin r-base to 3.3.1-1 (3.3.1-3 breaks it)

avoid creation of intermediate shell in start-notebook.sh

Adds crayon to the r notebook image

add tensorflow-notebook in the diagram

Add jupyter/tensorflow-notebook image

update README.md

update README

Update `tini` to `v0.10.0`

Add a generic start.sh script to images

Upgrade hdf5 and h5py conda packages

This package version includes the license file (LICENSE.txt).

Disable `conda` auto-update

* Update doc in base-notebook to describe use case
* Rebase start-notebook.sh on it

Fixed errors in READMEs