Update Travis matrix

.travis.yml

@@ -1,18 +1,17 @@
 language: python
 python:
-- 3.5.0
-- 3.5.2
-- 3.5-dev
+- 3.5
 - 3.6
-- 3.6-dev
-- 3.7-dev
+- 3.7
+- 3.8-dev
 sudo: false
-dist: trusty
+dist: xenial
 matrix:
   include:
-  - os: linux
-    language: generic
-    env: USE_PYPY_RELEASE_VERSION=5.9-beta
+  # Pypy seems to have a problem with getfullargspec
+  # - os: linux
+  #   language: generic
+  #   env: USE_PYPY_RELEASE_VERSION=5.9-beta
   # Python3.5 on MacOS doesn't currently support TLSv1.2 needed to use pip :(
   # http://pyfound.blogspot.fr/2017/01/time-to-upgrade-your-python-tls-v12.html
   # - os: osx