Fix: Replace License with the valid GPLv3 (#51)

Author: supcik

setup.py

@@ -49,7 +49,7 @@ def read(*names, **kwargs):
         # http://pypi.python.org/pypi?%3Aaction=list_classifiers
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
-        'License :: OSI Approved :: GNU GENERAL PUBLIC LICENSE',
+        'License :: OSI Approved :: GNU General Public License v3 (GPLv3)',
         'Operating System :: Unix',
         'Operating System :: POSIX',
         'Operating System :: Microsoft :: Windows',