Use outline-path-completion as org-goto-interface.

This uses the same interface as refile, and, because I have
org-completion-use-ido set to t, it uses IDO. Makes more sense to me,
although the default may be more powerful.
Remove old TiddlyWiki-related hacks.
Add TiddlyWiki-mode skeleton.
Add tid-mode.el to load-path, and require.
Add tiddocs.fish function.
Better tid-mode docs.