travis: update number of OS tested

.travis.yml

@@ -2,7 +2,6 @@ language: python
 python:
   - "2.7"
 sudo: required
-dist: trusty
 compiler:
   - gcc
 # - clang
@@ -15,9 +14,20 @@ env:
     - DO_COVERAGE_ON_BRANCH="master;release"
     - DO_CPPCHECK_ON_BRANCH=""
     - DO_INSTALL_DOC_EXCEPT_ON_BRANCH=""
-  matrix:
-    - BUILDTYPE=Release
-    - BUILDTYPE=Debug
+
+jobs:
+  include:
+    - dist: xenial
+      env:
+        matrix:
+          - BUILDTYPE=Release
+          - BUILDTYPE=Debug
+    - dist: trusty 
+      env:
+        matrix:
+          - BUILDTYPE=Release
+          - BUILDTYPE=Debug
+
 notifications:
   email:
     - pinocchio-build@laas.fr