Removed the calculator.py and parser.py as they are no longer needed.

The application will now use gtk and pyGtk to manage the application.
Removed the venv folder as virtual environment is no longer required for this
application. The original plan was to use kivy and pygame for managing the
application, but the plan has changed and will now be using gtk and pyGtk
for application management.

                                                 w be using gtk and pyGtk