Removing double call to model.views.push(view) in WidgetManager.
Pop child view from child_model.view in delete_child_view
Remove model from WidgetManager._model on comm:close.
Fixed bugs in displayed event triggering for containers
Removed log statement
Merge pull request #15 from jdfreder/widget-fixes

Widget fixes
Merge pull request #5896 from ellisonbg/widget-fixes

Widget fixes