Add __main__.py file

This file is used as a console entry point in the packaged version of the
application. It simply redirects all arguments to the invoke command, which
does all the work.

setup.py

@@ -46,7 +46,7 @@ setup(
     install_requires=install_requires,
     entry_points={
         'console_scripts': [
-            'wger = wger.main:main',
+            'wger = wger.__main__:main',
         ],
     },
 )