feat(build): use npm ci, it's faster then yarn (valor-software#4059)

.gitignore

@@ -3,7 +3,6 @@
 /node_modules
 /bower_components
 yarn.lock
-package-lock.json
 
 # IDEs and editors
 /.idea

.npmrc

@@ -1,2 +1 @@
 save-exact = true
-package-lock=false

.travis.yml

@@ -1,6 +1,6 @@
 sudo: false
 language: node_js
-node_js: "8"
+node_js: "9"
 
 notifications:
   email: false
@@ -41,7 +41,8 @@ before_install:
   - rm -rf node_modules/ngx-bootstrap
 
 install:
-  - npm install > /dev/null
+  - npm i -g [email protected]
+  - npm ci > /dev/null
   - npm run build > /dev/null
   - if [[ "$NGV" == "latest" ]]; then  ./scripts/ci/npm-ng-latest.sh; fi
   - if [[ "$NGV" == "next" ]]; then  ./scripts/ci/npm-ng-next.sh; fi
@@ -57,10 +58,11 @@ jobs:
   include:
 # precache npm and apt dependencies
     - stage: precache
-      install: npm install > /dev/null
+      install:
+        - npm i -g [email protected]
+        - npm ci > /dev/null
       script: true
       addons:
-        firefox: latest
         chrome: stable
         apt:
           sources: