FIX TreeEditor should release listeners to root node object

With Qt, when hide_root==True, to root node is assigned to
the tree's "invisibleRootItem", and listeners are added
as usual on the root node object.

However, when disposing the TreeEditor, the listener was
not released. This commit fixes that. This issue caused
a traceback when using Mayavi's "engine view", then closing
the "engine view" before exiting the application.
Merge pull request #90 from enthought/fix-tree-editor-listeners

FIX TreeEditor should release listeners to root node object
When creating the notebook, take account of 'selected' trait to set the default tab to be opened
Move selected handling outside of creation loop
Update traitsui/qt4/list_editor.py

minor code formatting change
Merge pull request #91 from enthought/fix_selected

When creating the notebook, take account of 'selected' trait to set the ...
Avoid qt traceback when clipboard has no python data object.
qt:tree_editor: prevent errors on drag-move of items.

QTreeWidgetItem does not have equality operator implemented,
so we check against id().
Verification: traitsui/examples/demo/Standard_Editors/TreeEditor_demo.py
 - Drag any employee from 'Scientific' to 'Business' dept.
Qt:tree_editor: prevent NoneType error on drag over top level item

Verification: traitsui/examples/demo/Standard_Editors/TreeEditor_demo.py
 - Drag any file from file-browser (finder/explorer/nautilus)
   over the top level node labelled 'Enthought'
Merge pull request #92 from pankajp/pymimedata-coerce-no-instance

Avoid qt traceback on drag/drop/clipboard operations.
Use tokenize module to grab the module docstring.

Iterating through the source and looking for triple quotes is buggy.
qt:clipboard: Catch TypeError from pickle.

Pickle unfortunately raises TypeError in case of methods which
it cannot pickle instead of raising PickleError, so we now catch
both.
Merge pull request #95 from pankajp/clipboard-pickle-typeerror

qt:clipboard: Catch TypeError from pickle.
Fix traitsui examples.

There were custom complaints that examples didn't run. This  was because
some examples don't call `configure_traits`. Also, some examples wouldn't
run on Qt; this fixes *some* of the compatibility issues.
Remove modal behavior from top-level examples.

Creating modal dialogs at the top level causes Qt windows to hang (and
doesn't really make sense). Note that the demo app creates an instance
editor with `kind='modal'` (see traitsui.extras.demo.ModalDemoButton),
so removing this from the example does not affect the demo app.
Add test to check that initial comment is handled correctly.
Use splitlines instead of split('\n')
Merge pull request #94 from enthought/fix-module-docstring-parsing

Demo code: Use tokenize module to grab the module docstring.
Rename wx.Color to wx.Colour.

Aliasing of Color names was removed from wxPython 2.9.
Merge pull request #101 from enthought/fix/wx-color-name

Rename wx.Color to wx.Colour.