Add breadcrumbs

[ZedThree]

Breadcrumbs are a navigation aid, and look like:

Home > Applications > Filaments

They're important for a) navigation and b) SEO.
There's already a styling in the materialize.css: http://materializecss.com/breadcrumbs.html

It looks like there's a couple of gems/plugins, so shouldn't be too tricky to implement.

[ZedThree]

Actually, our current structure is very flat so there's no need for this. Also, really hard to get looking good, it turns out...