Gifs are not rendering in the documentation

[luisfpereira]

This issue results from the replacement of image/png by image/gif in the field data of outputs in the jupyter notebook.

Potentially related with updates in ipython or related libraries.

[luisfpereira]

Hackily addressed in 867bf64 by hacking nbconvert (see https://github.com/luisfpereira/nbconvert/tree/gif).

See spatialaudio/nbsphinx#650 for discussions on a potential general solution.

Current solution is undesirable.

[luisfpereira]

Solved with monkey patching in d8b76bf.