PNGs missing from Readme

[cormullion]

I can't see thetiny_depgraph.png images in the Readme:

The Markdown is:

![tiny_depgraph](./test/references/Zarate/direct/tiny_depgraph.png 
 "tiny_depgraph") | ![tiny_depgraph](./test/references/Zarate/paths/tiny_depgraph.png "d") |

[oxinabox]

they all seem to be there for me

[thchr]

The references in the top row of the table are gone, i.e., the references to
./test/references/Zarate/direct/tiny_depgraph.png and ./test/references/Zarate/paths/tiny_depgraph.png were missing.

It seems tiny_depgraph got accidentally removed in #25. I've readded them as an unrelated part of #31.