Added an entry in release notes for keysort cythonization
Added an entry in release notes for keysort cythonization

FrancescAlted/PyTables,jennolsen84/PyTables,andreabedini/PyTables,FrancescAlted/PyTables,FrancescAlted/PyTables,PyTables/PyTables,tp199911/PyTables,rabernat/PyTables,rdhyee/PyTables,mohamed-ali/PyTables,jennolsen84/PyTables,gdementen/PyTables,rabernat/PyTables,tp199911/PyTables,dotsdl/PyTables,gdementen/PyTables,PyTables/PyTables,mohamed-ali/PyTables,avalentino/PyTables,gdementen/PyTables,mohamed-ali/PyTables,avalentino/PyTables,jennolsen84/PyTables,rabernat/PyTables,joonro/PyTables,rdhyee/PyTables,gdementen/PyTables,rdhyee/PyTables,joonro/PyTables,dotsdl/PyTables,andreabedini/PyTables,joonro/PyTables,dotsdl/PyTables,PyTables/PyTables,dotsdl/PyTables,rabernat/PyTables,tp199911/PyTables,joonro/PyTables,avalentino/PyTables,andreabedini/PyTables,jennolsen84/PyTables,tp199911/PyTables,andreabedini/PyTables,mohamed-ali/PyTables,rdhyee/PyTables