message: Check that we don't depend on newer dependencies
  Ensure we can still run with the oldest dependencies that we say we can
  run with.
diff: @@ -3,6 +3,16 @@ services:
  - mongodb
  node_js:
  - 6
  +env:
  + - USE_OLDEST_NPM_VERSIONS=0
  + - USE_OLDEST_NPM_VERSIONS=1
  +before_install:
  + - |
  + if [ $USE_OLDEST_NPM_VERSIONS -eq 1 ]
  + then
  + # Test against oldest allowed versions in package.json - Use sed to remove ^ characters
  + sed -i 's/"\^/"/g' package.json
  + fi
  script:
  - npm test
  - npm run coveralls
  