Travis CI: Test on Python 3.8 production release

Also drop the EOL Python 3.4  @hugovk Your review please.
diff --git a/.travis.yml b/.travis.yml
index ecce033..a7102d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,22 +2,20 @@
 
 language: python
 
-sudo: false
-
 cache: pip
 
 matrix:
   include:
     - python: 2.7
       env: TOXENV=py27
-    - python: 3.4
-      env: TOXENV=py34
     - python: 3.5
       env: TOXENV=py35
     - python: 3.6
       env: TOXENV=py36
     - python: 3.7
       env: TOXENV=py37
+    - python: 3.8
+      env: TOXENV=py38
     - python: 3.8-dev
       env: TOXENV=py38
     - python: pypy