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)

まず、現在の docs.python.org のホスティングとビルドプロセスを確認し、次に実験的な python.readthedocs.io のセットアップと比較してください。リリース履歴、Python 2.0 やその他の古いバージョン、そして複数のバージョン、言語、形式にまたがるとされているビルド負荷に特に注意してください。これらの要件を維持し、PSF とホスティングのトレードオフを解決する具体的な移行計画があれば完了とします。