Run tests against Python 3.7 and pypy 6.0

.travis.yml

@@ -1,11 +1,13 @@
+dist: xenial
 language: python
 python:
   - "2.7"
   - "3.4"
   - "3.5"
   - "3.6"
-  - "pypy"  # PyPy2 5.8.0
-  - "pypy3" # Pypy3 5.8.0-beta0
+  - "3.7"
+  - "pypy2.7-6.0"
+  - "pypy3.5-6.0"
 install: pip install tox-travis
 script:
   - tox

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py34, py35, py36, pypy, pypy3
+envlist = py27, py34, py35, py36, py37, pypy, pypy3
 skip_missing_interpreters=true
 
 [travis]
@@ -7,6 +7,7 @@ skip_missing_interpreters=true
 3.4 = py34
 3.5 = py35
 3.6 = py36
+3.7 = py37
 pypy = pypy
 pypy3 = pypy3