Bump PyPy version in Travis CI to the latest 7.1.1

Author: webknjaz

.travis.yml

@@ -4,8 +4,8 @@ python:
   # To see supported options, run:
   #   s3cmd ls s3://travis-python-archives/binaries/ubuntu/16.04/x86_64/
   # We put pypy first, b/c for tests they're the slowest
-  - pypy2.7-6.0
-  - pypy3.5-6.0
+  - pypy
+  - pypy3
   - 2.7
   - 3.4
   - 3.5