Update stylelint and remove node 6 from test-runners

.circleci/config.yml

@@ -49,11 +49,6 @@ templates:
         path: /tmp/artifacts
         destination: /artifacts
 jobs:
-  build-linux-node-v6:
-    docker:
-      - image: node:6
-    working_directory: ~/repo-linux-node-v6
-    steps: *build-steps
   build-linux-node-v8:
     docker:
       - image: node:8
@@ -70,14 +65,6 @@ jobs:
       - image: node:11
     working_directory: ~/repo-linux-node-v11
     steps: *build-steps
-  build-osx-node-v6:
-    macos:
-      xcode: "9.0"
-    dependencies:
-      override:
-        - brew install node@6
-    working_directory: ~/repo-osx-node-v6
-    steps: *build-steps
   build-osx-node-v8:
     macos:
       xcode: "9.0"
@@ -107,11 +94,9 @@ workflows:
   version: 2
   build:
     jobs:
-      - build-linux-node-v6
       - build-linux-node-v8
       - build-linux-node-v10
       - build-linux-node-v11
-      - build-osx-node-v6
       - build-osx-node-v8
       - build-osx-node-v10
       - build-osx-node-v11