Use npm ci instead of npm install

Author: smashwilson

.travis.yml

@@ -9,6 +9,8 @@ notifications:
 node_js:
   - "10.2.1"
 
+install: npm ci
+
 script: ./bin/npm test
 
 git:

appveyor.yml

@@ -12,7 +12,7 @@ environment:
 install:
   - ps: Install-Product node $env:nodejs_version $env:platform
   - npm install -g npm
-  - npm install
+  - npm ci
 
 build: off