Remove unnecessary parens after 'return' keyword

setup.py

@@ -7,7 +7,7 @@ def extract_version():
       with open(path.join('pydtn', '__init__.py')) as f:
             for line in f:
                   if line.startswith('__version__'):
-                        return(line.split("'")[1])
+                        return line.split("'")[1]
 
 def extract_requirements():
       with open('requirements.txt') as f: