Drop python 3.3 from setup.py

Author: dstansby

setup.py

@@ -125,7 +125,6 @@
     'Programming Language :: Python',
     'Programming Language :: Python :: 2.7',
     'Programming Language :: Python :: 3',
-    'Programming Language :: Python :: 3.3',
     'Programming Language :: Python :: 3.4',
     'Programming Language :: Python :: 3.5',
     'Programming Language :: Python :: 3.6',