Merge branch 'bug-109-reopened' into develop

.travis.yml

@@ -1,24 +1,24 @@
+# autho: Herbert Koelman
+# created on: 1/6/2019
 os: linux
-# dist: trusty
+
+# use Ubuntu Xenial (version 16)
+# This comes with cmake 3.11 which is required to build GoogleTest
+dist: xenial
 language: cpp
 compiler: gcc
 
+# Run travis on these branches only...
 branches:
   only:
     - master
     - develop
 
 addons:
   apt:
-    sources:
-      - ubuntu-toolchain-r-test
     packages:
       - doxygen
       - graphviz
-      - g++-6
-env:
-  global:
-    - CXX=/usr/bin/g++-6 CC=/usr/bin/gcc-6
 
 script:
   - mkdir cmake-build