Use the github URL in setup

wger.de is just a specific instance, when installing the package the link to
the source code is more relevant.

setup.py

@@ -25,7 +25,7 @@
     description='FLOSS workout, fitness and weight manager/tracker written with Django',
     long_description=long_description,
     version=get_version(),
-    url='https://wger.de',
+    url='https://github.com/wger-project',
     author='Roland Geider',
     author_email='[email protected]',
     license='AGPL3+',