Update classifiers to reflect supported Python versions

Author: davehunt

setup.py

@@ -27,10 +27,7 @@
           'Topic :: Software Development :: Testing',
           'Topic :: Utilities',
           'Programming Language :: Python',
-          'Programming Language :: Python :: 2.6',
           'Programming Language :: Python :: 2.7',
-          'Programming Language :: Python :: 3.3',
-          'Programming Language :: Python :: 3.4',
-          'Programming Language :: Python :: 3.5',
+          'Programming Language :: Python :: 3.6',
           'Programming Language :: Python :: Implementation :: CPython',
           'Programming Language :: Python :: Implementation :: PyPy'])