green.core.GreenInvitation: return the notifications captured

darcs-hash:20090416123807-b2873-029c412826d91da2be2b9279e30c53555728b11e
session2: add end() method and 'state' attribute

darcs-hash:20090416123850-b2873-98bbbb7eff9342192dd6f00b00e8a51276fbb6c0