added comments and renamed variables
getting ready to refactor the regex for scanning the text.
I tried very hard to clairify the regex, but failed.  It's just one of those things that hopefully no one ever needs to look back on.
refactored if statement to a case when.  It looks nice.
@bbtree is now responsible for @tags_list
in the middle of refactoring @bbtree_current_node to be of the type TagNode... I'm not sure if this will actually work to get bbtree the escalate_bbtree and retrogress_bbtree methods, but it's worth a shot.
made BBTree accept a dictionary of tags so constraints on parent nodes can be looked up from within BBTree.  And misc refactoring.
tidy'd up tag_collection
tidy'd up bbtree.rb
comments
removed debug thing
realized the need for to add a new instance variable for the final tree that is being built up.  I just made comments.