Update classifiers to drop Python 3.4 and add Python 3.7 (#5702)

diff --git a/setup.py b/setup.py
index b813a18..acd4ff5 100644
--- a/setup.py
+++ b/setup.py
@@ -80,9 +80,9 @@
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Operating System :: OS Independent',
         'Topic :: Internet',
     ],