• Release the GIL in the Python package, so that it can be used efficiently
in multithreaded applications.
• Improved performance for the "Ward" method with vector input.
• The "members" parameter in the R interface is now treated as a double
array, not an integer array as before. This was a slight incompatibility
with the stats::hclust function. Thanks to Matthias Studer, University of
Geneva, for pointing this out.