message: Add Python 3.7 to setup.py classifiers
diff: @@ -51,6 +51,7 @@ setup(
  "License :: MIT",
  "Programming Language :: Python :: 3 :: Only",
  "Programming Language :: Python :: 3.6",
  + "Programming Language :: Python :: 3.7",
  "Operating System :: MacOS :: MacOS X",
  "Operating System :: POSIX :: Linux",
  ],
  