Added wxPython to the installation instructions.
Added wxPython to the installation instructions.

Added wxPython to the installation instructions as it is not automatically installed or checked by `setup.py`.
senthilmm/Gooey,jschultz/Gooey,joaquins/Gooey,codingsnippets/Gooey,partrita/Gooey,chriskiehl/Gooey,alexkolar/Gooey,IvanoAlvino/Gooey,s4n7h0/Gooey