Update readme to v0.4.0 (#604)
Update readme to v0.4.0 (#604)

This patch changes the readme so that it matches the v0.4.0 release.
* Redesign example gifs table (add new augmenters, add "see also" rows, add per augmenter a link to the overview page)
* Remove the list of augmenters at the bottom of the readme. It is redundant with the gifs table and RTD docs.
* Remove example on how to use hooks. They aren't very necessary anymore.
* Update the list of authors in the "Citation" section.
* Add v0.4.0 to "recent changes" section.
* Remove unnecessary commands from the "installation" section.
aleju/imgaug,aleju/imgaug,aleju/ImageAugmenter