Update weather data example

[fmaussion]

• Closes #xxxx
• Tests added / passed
• Passes git diff upstream/master | flake8 --diff
• Fully documented, including whats-new.rst for all changes and api.rst for new API

For some reason a plot from the examples was rendered statically instead of live. This is now fixed, together with an update of pandas which prevents reshaping operations on indexes.

Tested here

[shoyer]

Thanks @fmaussion! I think this dates to the old days of RTD (before conda support) when getting things to build correctly was difficult.