Add a list of developed (by ReproFellows) materials

[yarikoptic]

a follow up to #240 in that the idea is related: add references to training materials (curriculums, slides, etc) to the website. Could go to training page or to fellows but be referenced (explicitly) from training.

[chaselgrove]

The full list may be handled elsewhere (reproinventory, in whatever form it takes?) but there may well be a pointer from the core site.