#53 transparent background for StaticText

[Kevin Altis]

Figure out how to do a StaticText widget that can have
a transparent background, so that the text
will "float" over any image on the background.
Transparency isn't necessary for solid backgrounds
since the StaticText widget can use the same
background color or show the background color by
default, but it doesn't help for images behind the
text.

EVT_ERASE_BACKGROUND(widget, lambda evt: None)

doesn't work for wxStaticText