Here is a pretty minimal patch to expose bjunk and bpopular as attributes and document them along with b2j, which is already exposed but not documented.

I suppose the proposed paragraph could be formatted as a list, perhaps after 
   ":class:`SequenceMatcher` objects have the following methods:"
with 'methods' expanded to 'attributes and methods'. But I do not know how to do that and personally prefer what I wrote.

However, Georg, I am adding you as nosy so you can comment on the doc addition *before* I commit this tomorrow, to get it in the beta.

Still to do: improve the doctests, including those added as part of #2986, to use the exposed sets (they are already implicitly tested by the existing tests); deprecate the two obsolete function attributes, as discussed on pydev.

The docstrings and code comments might stand revision, and there is an XXX todo in the doc yet.