build: support Node.js 8.x

Author: dougwilson

.gitignore

@@ -2,3 +2,4 @@
 coverage
 node_modules
 npm-debug.log
+package-lock.json

.travis.yml

@@ -11,12 +11,15 @@ node_js:
   - "5.12"
   - "6.11"
   - "7.10"
+  - "8.4"
 sudo: false
 dist: precise
 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 != '0.6' || npm rm --save-dev nyc"
   - "test $TRAVIS_NODE_VERSION != '0.8' || npm rm --save-dev nyc"