update setup.py, tmuxp supports python 3.3

Author: tony

setup.py

@@ -54,6 +54,7 @@ def requirements(f):
         'Intended Audience :: Developers',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3.3',
         "Topic :: Utilities",
         "Topic :: System :: Shells",
     ],