Added 3.7 support notice.

Author: rohe

setup.py

@@ -64,6 +64,7 @@ def run_tests(self):
         "License :: OSI Approved :: Apache Software License",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Topic :: Software Development :: Libraries :: Python Modules"],
     install_requires=[
         "pyyaml>=5.1.0",