constructs are called initialize
get rid of the footer field
don't generate topic classes on-the-fly

Just set :topic.
add :index_fill to IndexPage and compute it
get rid of the footer altogether
compute the sidebar
more :indexfill related changes
turn template into a variable
fix content filling: variable names
introduce Page#render
it's spelt :indexfill, not :index_fill
all_files should not include .gitignore
clarify that we're mapping filenames to get *_pages
compute the sidebar and call render with it
correct the template for ContentPage