Tweak for Python 3.7

.travis.yml

@@ -1,6 +1,7 @@
 language: python
 python:
   - "3.6"
+  - "3.7"
 install:
  - pip install -r requirements.txt
  - pip install -r dev-requirements.txt

setup.py

@@ -61,6 +61,7 @@ setup(
         "License :: OSI Approved :: ISC License (ISCL)",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
     ],