Rename designer startup script to 'pygubu-designer'. fixes alejandroautalan#20

Author: alejandroautalan

bin/pygubu bin/pygubu-designer

@@ -132,7 +132,7 @@ def __init__(self, master):
             'images/widgets/22x22/*.gif', 'ui/*.ui',
             'locale/*/*/*.mo'],
     },
-    scripts=["bin/pygubu"],
+    scripts=["bin/pygubu-designer"],
     cmdclass={
         'install': CustomInstall,
     },