make wx backends compatible with wxPython-Phoenix

This is based on the comments made to my previous PR for this.

Note that wxPython Phoenix snapshots can now be installed with pip:
pip install -U --pre -f http://wxpython.org/Phoenix/snapshot-builds/ wxPython_Phoenix 
On 12/5/2014 16:42, Benjamin Root wrote:
>
> In examples/user_interfaces/embedding_in_wx2.py:
>
> >
> > +class App(WIT.InspectableApp):
>
> This is new to me. Is this what wx users are supposed to use now? I 
> want to make sure I get this right for my book that I am about to publish.
>
The WIT 
(http://wxpython.org/Phoenix/docs/html/lib.mixins.inspection.html#module-lib.mixins.inspection) 
allows debugging of the running application to e.g. figure out problems 
with sizers and as it has a PyCrust pane which can also be very useful 
in debugging, I use that setup in all my stuff.

so it should be the above or:

class App(wx.App):

but no longer use wx.PySimpleApp.

Werner