Implement diff method in DefaultKeySet
Implement diff method in DefaultKeySet

lrytz/scala,martijnhoekstra/scala,martijnhoekstra/scala,scala/scala,scala/scala,scala/scala,martijnhoekstra/scala,scala/scala,martijnhoekstra/scala,lrytz/scala,lrytz/scala,scala/scala,lrytz/scala,martijnhoekstra/scala,scala/scala,lrytz/scala,lrytz/scala,martijnhoekstra/scala