QObjects leaked by test suite

Here's a summary of the `QObjects` leaked by the test suite, under Python 2.7 / PyQt / OS X 10.9.5. (Under PySide, there are many more, but PySide is known to handle reference counting badly.)
```
QObjects at start of test run: {'QApplication': 2, 'QClipboard': 1}.
test_group_content_at_startup (pyface.tasks.tests.test_dock_pane_toggle_group.DockPaneToggleGroupTestCase) changed QObject counts. added: {'QWidget': 3, '_EventFilter': 1, 'QMainWindow': 1, 'QDockWidget': 2, 'QStackedWidget': 1}.
test_react_to_dock_pane_added (pyface.tasks.tests.test_dock_pane_toggle_group.DockPaneToggleGroupTestCase) changed QObject counts. added: {'QWidget': 3, '_EventFilter': 1, 'QMainWindow': 1, 'QDockWidget': 2, 'QStackedWidget': 1}.
test_react_to_dock_pane_removed (pyface.tasks.tests.test_dock_pane_toggle_group.DockPaneToggleGroupTestCase) changed QObject counts. added: {'QWidget': 3, '_EventFilter': 1, 'QMainWindow': 1, 'QDockWidget': 2, 'QStackedWidget': 1}.
test_ok (pyface.tests.test_about_dialog.TestAboutDialog) changed QObject counts. added: {'QDialog': 1}.
test_parent (pyface.tests.test_about_dialog.TestAboutDialog) changed QObject counts. removed: {'QDialog': 1}.
test_renamed_ok (pyface.tests.test_about_dialog.TestAboutDialog) changed QObject counts. added: {'QDialog': 1}.
test_activate (pyface.tests.test_application_window.TestApplicationWindow) changed QObject counts. removed: {'QDialog': 1}.
test_menubar (pyface.tests.test_application_window.TestApplicationWindow) changed QObject counts. added: {'QAction': 5}.
test_statusbar (pyface.tests.test_application_window.TestApplicationWindow) changed QObject counts. added: {'QStatusBar': 1}.
test_toolbar (pyface.tests.test_application_window.TestApplicationWindow) changed QObject counts. added: {'_ToolBar': 1, 'QAction': 5}.
test_set_object_data (pyface.tests.test_clipboard.TestClipboard) changed QObject counts. added: {'QMimeData': 1}.
test_set_text_data (pyface.tests.test_clipboard.TestClipboard) changed QObject counts. removed: {'QMimeData': 1}.
test_cancel (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QMessageBox': 1, 'QPushButton': 3}.
test_cancel_renamed (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 3}.
test_close (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.removed: {'QMessageBox': 1}.
test_close_with_cancel (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 3}.
test_create (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 1}.
test_create_cancel (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 3}.
test_create_cancel_default (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 3}.
test_create_cancel_renamed (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 3}.
test_create_image (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_create_no_renamed (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_create_parent (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_create_yes_default (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_create_yes_renamed (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_no (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QMessageBox': 1, 'QPushButton': 2}.
test_parent (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.removed: {'QMessageBox': 1}.
test_renamed_no (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QMessageBox': 1, 'QPushButton': 2}.
test_renamed_yes (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_yes (pyface.tests.test_confirmation_dialog.TestConfirmationDialog) changed QObject counts. added: {'QPushButton': 2}.
test_accept (pyface.tests.test_dialog.TestDialog) changed QObject counts. removed: {'QMessageBox': 1}.
test_help (pyface.tests.test_dialog.TestDialog) changed QObject counts. added: {'QDialog': 1}.
test_nonmodal_close (pyface.tests.test_dialog.TestDialog) changed QObject counts. removed: {'QDialog': 1}.
test_ok (pyface.tests.test_dialog.TestDialog) changed QObject counts. added: {'QDialog': 1}.
test_reject (pyface.tests.test_dialog.TestDialog) changed QObject counts. removed: {'QDialog': 1}.
test_renamed_cancel (pyface.tests.test_dialog.TestDialog) changed QObject counts. added: {'QDialog': 1}.
test_size (pyface.tests.test_dialog.TestDialog) changed QObject counts. removed: {'QDialog': 1}.
test_ok (pyface.tests.test_message_dialog.TestMessageDialog) changed QObject counts. added: {'QMessageBox': 1}.
test_parent (pyface.tests.test_message_dialog.TestMessageDialog) changed QObject counts. removed: {'QMessageBox': 1}.
test_error (pyface.tests.test_message_dialog.TestMessageDialogHelpers) changed QObject counts. added: {'QMessageBox': 1}.
test_can_cancel (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 1}.removed: {'QMessageBox': 1}.
test_change_message (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_create (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 1}.
test_incomplete_update (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_show_time (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 4}.
test_update (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_update_degenerate (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_update_show_time (pyface.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 4}.
test_error_ok (pyface.tests.test_window.TestWindow) changed QObject counts. added: {'QMessageBox': 1}.
test_information_accept (pyface.tests.test_window.TestWindow) changed QObject counts. removed: {'QMessageBox': 1}.
test_information_ok (pyface.tests.test_window.TestWindow) changed QObject counts. added: {'QMessageBox': 1}.
test_open_close (pyface.tests.test_window.TestWindow) changed QObject counts. removed: {'QMessageBox': 1}.
test_warning_ok (pyface.tests.test_window.TestWindow) changed QObject counts. added: {'QMessageBox': 1}.
test_active_editor_after_focus_change (pyface.ui.qt4.tasks.tests.test_split_editor_area_pane.TestEditorAreaWidget) changed QObject counts. removed: {'QMessageBox': 1}.
/Users/mdickinson/.edm/envs/pyface-test-2.7-pyqt/lib/python2.7/site-packages/pyface/ui/qt4/mimedata.py:49: RuntimeWarning: Could not pickle dragged object at 0x120547f50>, using application/x-ets-qt4-instance-no-pickle mimetype instead
self.NOPICKLE_MIME_TYPE), RuntimeWarning)
test_change_message (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_change_message_trait (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_create (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 1}.
test_show_percent (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 1}.
test_show_time (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QProgressBar': 1, 'QLabel': 4}.
test_update (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 1}.
test_update_show_time (pyface.ui.qt4.tests.test_progress_dialog.TestDialog) changed QObject counts. added: {'QLabel': 4}.
test_capture_errors_on_error (pyface.ui.qt4.util.tests.test_modal_dialog_tester.TestModalDialogTester) changed QObject counts. added: {'QTimer': 3, '_FutureCall': 2}.
QObjects at end of test run: {'_ToolBar': 1, 'QMainWindow': 3, 'QDockWidget': 6, 'QStackedWidget': 3, 'QClipboard': 1, 'QLabel': 27, 'QPushButton': 41, 'QAction': 10, '_FutureCall': 2, 'QStatusBar': 1, '_EventFilter': 3, 'QWidget': 9, 'QApplication': 2, 'QTimer': 3, 'QProgressBar': 6}.
```