Make it easier to find tut docs

[ceedubs]

I remembered that there were some useful atto tut docs, but after the microsite transition I found them a little difficult to locate and probably wouldn't have kept looking for them if I didn't know that they were there somewhere.

Currently it looks like the only real way to get to them from the site is to click on "Documentation" in the top right. For some reason I had assumed that this would take me to the API ScalaDocs, which might just be a me thing. However, I think that at a minimum it would be helpful to link to the tut docs in the readme/index body.