I've cleaned up the namespace of `ip_diffim` by adding `_all_` to modules where it was missing, and Sphinx now builds with automodapi turned on. It does generate many warnings about the documentation formatting, but I believe those are best fixed when the docstrings are converted over to numpydoc.

Looks good in principle. The only necessary change is fix up the location of _all_ to follow the Developer Guide.

I assume you've checked that the additions of _all_ are good with `stack-os-matrix` too, right? Other than that, good to go.

I moved the `_all_` declarations above the imports, and the rebased changes pass Jenkins.