Merge pull request googleapis#2671 from dhermes/fix-2350

Adding Python 3.5 on Travis.

Author: dhermes

.travis.yml

@@ -1,12 +1,20 @@
 language: python
 sudo: false
 
+addons:
+  apt:
+    sources:
+    - deadsnakes
+    packages:
+    - python3.5
+
 install:
   - pip install --upgrade pip tox
 
 script:
   - python2.7 scripts/run_unit_tests.py
   - python3.4 scripts/run_unit_tests.py
+  - python3.5 scripts/run_unit_tests.py
   - python scripts/run_unit_tests.py --tox-env cover
   - tox -e lint
   - tox -e system-tests