Fix handling for long numeric list item tags (e.g. "10000. foo")

Fixing thise required two changes

10000. When you've discovered an enumerated list item with a long
       identifier set clip to the length of the identifier so that it
       all gets trimmed off properly.
42. When you're looking for additional paragraphs to include with that
    item use the standard indent of 4, not the crazy long ident you
    used to trim the identifier.

Add a test for this case.

Fix another test for which the old code generated some whitespace
(which doesn't change the way the page looks in a browser but which
futzed up the exact matching in the test).
Another long number test, make sure that embedded lists work too.