commit package-lock.json to git to use npm ci

Author: gfx

.gitignore

@@ -2,7 +2,6 @@ node_modules/
 dist/
 dist.es5/
 build/
-package-lock.json
 .nyc_output/
 coverage/
 benchmark/sandbox.ts

.travis.yml

@@ -1,11 +1,14 @@
+# https://docs.travis-ci.com/user/languages/javascript-with-nodejs/
 language: node_js
 addons:
   firefox: latest
 node_js:
   - "lts/*"
   - "node"
 cache: npm
-before_install: npm install -g nyc codecov
+install:
+  - npm install -g nyc codecov
+  - npm ci
 script:
   - npm run test:browser:firefox
   - npm run test:cover