Switch to custom version of PyPy

Author: rmk135

.travis.yml

@@ -15,7 +15,10 @@ env:
   - TOXENV=py34
   - TOXENV=py35
   - TOXENV=pypy
-  - TOXENV=pypy3
+matrix:
+    include:
+      - python: pypy-5.3.1
+        env: TOXENV=pypy3
 notifications:
   slack:
     secure: QHOypFu1TxCmkbCeNSqY39Bdj+hxOnA7H0zpTZrxDouLFdD+Ah5cKHFOFjFULruCdRo+JI8vPN0fmgRviUcyFVjKbs/3sEEUNU//JJpBPDQB9Epdc8jVp1w1GDF4fN/ujg3XW19U6N1dORRQBFi5EuJn/seYErogIs6F/4G8nEstyTLWqZ7DgnVBMM5aUVuwDae+iUNTutWTvVwJVqS84JC2rFzsRmXc9RJou6/PljBGogE5t+RYHWWAzSodwf3fMIdC7nKk+U6p5IwaDd021vgqk6Dduhu5qum89KsV80hP97qTIiJO/bz5gX6S/DG4cjjXFo2ELZARcRdQ2G7PJBooomiMPW3OTm4uTIbjxDKSIlZm/miHjUVv/+Am5TYgYPnOqU9RlYxAGFbKmkOXDwgJK3nyK8s4hK19cGss3hbRPC7VWRXAaGmO6Yk+UH7wUAbAPSzXvLT/GXc8VlY276KIFVoBX0dLlqSLt/jHrVvKZL1djXKIEa1cDUA9rDqybn+/Oue0QF9ask34lNM2Uu/5IdMAUz8V/U7UHtlfoYFMOJIbgzjUHRLAcIx9+k908rHAOzkMnPns9rDHkJFgJaj3n6Q5HJpQUMwq89Lhb1NHry0nNRE5awtXio6cRcri/ApVxFA+juuyRS64y1Adi8Su/ENAw4CkVeURJuMOqPk=