Updated CHANGELOG.
Updated CHANGELOG.
New code contributed by Maria Cumplido (student of Juan
González-Meneses).  Juan's description: The old code computed some
sets called Ultra Summit Sets, while the new one computes Sets of
Sliding Circuits (which are in general the same as above, but not
always).
Removed some unused variables in new code.
Added credit to Maria Cumplido in README.  Updated CHANGELOG.