Fixed the license declaration in setup.py.

Author: marcusw

setup.py

@@ -16,7 +16,7 @@
     author_email='marcusw@cox.net',
     description='LEGO Mindstorms NXT Control Package',
     url='http://home.comcast.net/~dplau/nxt_python/, http://code.google.com/p/nxt-python/',
-    license='Gnu GPL v2',
+    license='Gnu GPL v3',
     packages=['nxt', 'nxt.sensor'],
     scripts=['scripts/nxt_push', 'scripts/nxt_test', 'scripts/nxt_filer'],
     long_description=ldesc