build: support Node.js 8.x

Author: dougwilson

.gitignore

@@ -1,2 +1,3 @@
 coverage
 node_modules
+package-lock.json

.travis.yml

@@ -10,11 +10,14 @@ node_js:
   - "5.12"
   - "6.11"
   - "7.10"
+  - "8.9"
 sudo: false
 cache:
   directories:
     - node_modules
 before_install:
+  # Skip updating shrinkwrap / lock
+  - "npm config set shrinkwrap false"
   # Setup Node.js version-specific dependencies
   - "test $TRAVIS_NODE_VERSION != '0.8' || npm rm --save-dev istanbul"
   - "test $(echo $TRAVIS_NODE_VERSION | cut -d. -f1) -ge 4 || npm rm --save-dev $(grep -E '\"eslint\\S*\"' package.json | cut -d'\"' -f2)"