message: Fix Travis CI tests to run in Node 8 again (and 10).
diff: language: node_js
  matrix:
  include:
  - - node_js: "9"
  + - node_js: "10"
  env: NPM_VERSION=""
  - node_js: "9"
  env: NPM_VERSION=""
  + - node_js: "8"
  + env: NPM_VERSION=""
  - node_js: "7"
  env: NPM_VERSION=""
  - node_js: "6"
  