Don't add plugin content dir to load path if main require failed
Keep track of what plugins are loaded
Use StandardError instead of Exception for parent class
Small refactor
Decide that macros should be expanded before template processing

Because otherwise the include macro will paste Markdown in the midst of HTML.
Change macro expander interface
Super-simplify Layout plugin
Use tmp dir for sass cache
Fix editor not being full
Remove theme-slab, it is no longer exemplary
Make visuals better for breadcrumbs
Include index file in tree
Fix include macro