DOC/BLD: host doc build artefacts of PRs
In scikit-learn it is possible to see the docs for a PR (see contributing guide: http://scikit-learn.org/stable/developers/contributing.html#documentation) because they build and upload it with circle-ci, and make it available from a canonical url, eg http://scikit-learn.org/circle?13937/documentation.html

Would be cool to do something similar for pandas. Certainly for PRs that rework part of the documentation, it is useful to check how it is looking.