chore(ci): move all CI from Node7 to Node8 (puppeteer#2938)

Node 8 is the current LTS. We should use it by default on all
our CIs.

.appveyor.yml

@@ -1,14 +1,14 @@
 environment:
   matrix:
     - nodejs_version: "6.12.3"
-    - nodejs_version: "7.10.1"
+    - nodejs_version: "8.11.3"
 
 build: off
 
 install:
   - ps: Install-Product node $env:nodejs_version
   - npm install
-  - if "%nodejs_version%" == "7.10.1" (
+  - if "%nodejs_version%" == "8.11.3" (
       npm run lint &&
       npm run coverage  &&
       npm run test-doclint

.ci/node7/Dockerfile.linux → .ci/node8/Dockerfile.linux

@@ -1,4 +1,4 @@
-FROM node:7.10.1
+FROM node:8.11.3
 
 RUN apt-get update && \
     apt-get -y install xvfb gconf-service libasound2 libatk1.0-0 libc6 libcairo2 libcups2 \

.cirrus.yml

@@ -12,9 +12,9 @@ task:
 
 task:
   matrix:
-    - name: node7 (linux)
+    - name: node8 (linux)
       container:
-        dockerfile: .ci/node7/Dockerfile.linux
+        dockerfile: .ci/node8/Dockerfile.linux
       xvfb_start_background_script: Xvfb :99 -ac -screen 0 1024x768x24
   install_script: npm install --unsafe-perm
   lint_script: npm run lint

.travis.yml

@@ -15,14 +15,14 @@ before_install:
   - "export DISPLAY=:99.0"
   - "sh -e /etc/init.d/xvfb start"
 script:
-  - 'if [ "$NODE7" = "true" ]; then npm run lint; fi'
-  - 'if [ "$NODE7" = "true" ]; then npm run coverage; fi'
-  - 'if [ "$NODE7" = "true" ]; then npm run test-doclint; fi'
+  - 'if [ "$NODE8" = "true" ]; then npm run lint; fi'
+  - 'if [ "$NODE8" = "true" ]; then npm run coverage; fi'
+  - 'if [ "$NODE8" = "true" ]; then npm run test-doclint; fi'
   - 'if [ "$NODE6" = "true" ]; then npm run unit-node6; fi'
 jobs:
   include:
-    - node_js: "7.10.1"
-      env: NODE7=true
+    - node_js: "8.11.3"
+      env: NODE8=true
     - node_js: "6.12.3"
       env: NODE6=true
 before_deploy: "npm run apply-next-version"
@@ -33,6 +33,6 @@ deploy:
     secure: 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
   on:
     branch: master
-    condition: "$NODE7 = true"
+    condition: "$NODE8 = true"
   skip_cleanup: true
   tag: next