Use npm ci instead of npm install (#336)

* dont write server_info.json either - second half of #318

* use npm ci

* update lockfile

* try this

.travis.yml

@@ -18,4 +18,4 @@ addons:
 install:
   - export DISPLAY=':99.0'
   - Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
-  - npm install
+  - npm ci || npm i

appveyor.yml

@@ -14,7 +14,7 @@ environment:
 
 install:
   - ps: Install-Product node $env:nodejs_version
-  - npm install
+  - npm ci
 
 test_script:
   - node --version && npm --version