- give absolute paths to imgsize() so it chills out on Cwd::getcwd() calls
- rip out App::WRT::MethodSpit's convenience accessors and just access
  elements of $self directly
- kill local_path()
- stop using a() in entry_markup()
- cache get_date_entries_by_depth() results
- swap out state vars for stashing things on $self in
  get_all_source_files()

This gets rendering the whole p1k3 repo back down in the neighborhood of
2.1 seconds, which is a lot more tolerable than 5 or 6.

It also kinda technically breaks the API, maybe, so I guess this'll be a
v5.0.0 after a while.