Added a CSS "hook" for detecting whether a node is collapsed or not.
Added a CSS "hook" for detecting whether a node is collapsed or not.

ecohealthalliance/tangelo,mathstuf/tangelo,Kitware/tangelo,ecohealthalliance/tangelo,ecohealthalliance/tangelo,Kitware/tangelo,mathstuf/tangelo,mathstuf/tangelo,Kitware/tangelo