Add py37 to classifiers

Author: childish-sambino

setup.py

@@ -50,6 +50,7 @@
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Topic :: Software Development :: Libraries :: Python Modules",
         "Topic :: Communications :: Telephony",
     ],