Add Python 3.7 to trove classifiers.

setup.py

@@ -1,7 +1,7 @@
 #! /usr/bin/env python
 # -*- coding: utf-8  -*-
 #
-# Copyright (C) 2012-2016 Ben Kurtovic <ben.kurtovic@gmail.com>
+# Copyright (C) 2012-2018 Ben Kurtovic <ben.kurtovic@gmail.com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -107,6 +107,7 @@ setup(
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Topic :: Text Processing :: Markup"
     ],
 )