Host the Python docs on ReadTheDocs

From time to time the discussion arise about moving docs.python.org to readthedocs, there's even an experimental python.readthedocs.io.

I think there's many pros and cons of using readthedocs.

I'd personally be in favor of it if we (the PSF) support them (the cpython Doc is a big one with a lot of traffic, it take around 24h of CPU to build all versions × languages with all PDF A4, PDF letter, HTML, plaintext, epub).

In the other hand it's not an easy task, among other things docs.python.org is not only about generating the docs but also hosting history:

• https://docs.python.org/release/ (this is all the tagged commits in the cpython repo)
• https://docs.python.org/2.0/ (yes we keep old versions, and I'm not willing to see this disapear)

Commencez par examiner l’hébergement et le processus de build actuels de docs.python.org, puis comparez-les avec la configuration expérimentale de python.readthedocs.io. Portez une attention particulière à l’historique des versions, à Python 2.0 et aux autres anciennes versions, ainsi qu’à la charge de build indiquée pour plusieurs versions, langues et formats. La tâche sera considérée comme terminée lorsqu’un plan de migration concret préservera ces exigences et résoudra les compromis entre la PSF et l’hébergement.