tweaked tests so they work even if debugging features are disabled.
INTERESTING:  I made an ugly recursive function go away by re-using a block-accepting method
cleaned up to_s method for BBTree and TagNode
fixed some sleepily made sloppy code the same night I made blunder.
debugging code now cleaned
implemented youtube link formatter.
cleaned out comments
cleaned up comments
removed pry reference and unused expression
moved #parse_youtube_id(url) into the TagSifter class... but my OS just crashed soft so the unit tests aren't working yet