message: travis use gcc8
diff: @@ -25,10 +25,11 @@ addons:
  packages:
  - build-essential
  - cython
  - #- g++-5
  + - g++-8
  + - gcc-8
  #- clang-3.9
  #env: CC=clang-3.9 CXX=clang-3.9
  -#env: CC=g++-5 CXX=g++-5
  +env: CC=gcc++-8 CXX=g++-8
  # command to install dependencies
  