Add documentation for weather update through Zapier.
Contains tests and fixtures for weather example.
With minor fixes, docs migration to Markdown, and
rebasing by Eeshan Garg.
I dug into why we never did this before, and it turns out we did, but
using `$.trim()` (which removes leading whitespace as well!). When
removing the `$.trim()` usage.
Fixes#3294.
rht
wizsid11
Tim Abbott
Tomasz Kolek