Drop node4 completely (#160)

.circleci/config.yml

@@ -3,12 +3,10 @@ workflows:
   version: 2
   tests:
     jobs: &workflow_jobs
-      - node4:
+      - node6:
           filters: &all_commits
             tags:
               only: /.*/
-      - node6:
-          filters: *all_commits
       - node8:
           filters: *all_commits
       - node9:
@@ -60,9 +58,9 @@ workflows:
               only: master
     jobs: *workflow_jobs
 jobs:
-  node4:
+  node6:
     docker:
-      - image: 'node:4'
+      - image: 'node:6'
         user: node
     steps: &unit_tests_steps
       - checkout
@@ -93,11 +91,6 @@ jobs:
           name: Submit coverage data to codecov.
           command: node_modules/.bin/codecov
           when: always
-  node6:
-    docker:
-      - image: 'node:6'
-        user: node
-    steps: *unit_tests_steps
   node8:
     docker:
       - image: 'node:8'
@@ -115,7 +108,7 @@ jobs:
     steps: *unit_tests_steps
   lint:
     docker:
-      - image: 'node:8'
+      - image: 'node:10'
         user: node
     steps:
       - checkout
@@ -137,7 +130,7 @@ jobs:
             NPM_CONFIG_PREFIX: /home/node/.npm-global
   docs:
     docker:
-      - image: 'node:8'
+      - image: 'node:10'
     steps:
       - checkout
       - run: *remove_package_lock
@@ -147,7 +140,7 @@ jobs:
           command: npm run docs
   sample_tests:
     docker:
-      - image: 'node:8'
+      - image: 'node:10'
         user: node
     steps:
       - checkout
@@ -174,7 +167,7 @@ jobs:
     working_directory: /home/node/bigtable-samples/
   system_tests:
     docker:
-      - image: 'node:8'
+      - image: 'node:10'
         user: node
     steps:
       - checkout
@@ -197,7 +190,7 @@ jobs:
           when: always
   publish_npm:
     docker:
-      - image: 'node:8'
+      - image: 'node:10'
         user: node
     steps:
       - checkout