bump to node8/npm5 -> update circleci config

- use official '8.9.4' docker images
- checksum package-lock.json to check cache
- replace (now unnecessary) install/dedupe/prune/install with
  a simple install (now with package-lock.json this does the right
  thing everytime ;)

Author: etpinard

.circleci/config.yml

@@ -3,25 +3,25 @@ version: 2.0
 # Inspired by:
 # https://github.com/CircleCI-Public/circleci-demo-workflows/blob/workspace-forwarding/.circleci/config.yml
 # https://circleci.com/docs/2.0/workflows/#using-workspaces-to-share-data-among-jobs
+#
+# For list of official CircleCI node.js images, go to:
+# https://hub.docker.com/r/circleci/node/tags/
 
 jobs:
   build:
     docker:
-      - image: circleci/node:6.10.3
+      - image: circleci/node:8.9.4
     working_directory: ~/plotly.js
     steps:
       - checkout
       - restore_cache:
           keys:
-            - v{{ .Environment.CIRCLE_CACHE_VERSION }}-deps-{{ .Branch }}-{{ checksum "package.json" }}
-            - v{{ .Environment.CIRCLE_CACHE_VERSION }}-deps-master-{{ checksum "package.json" }}
+            - v{{ .Environment.CIRCLE_CACHE_VERSION }}-deps-{{ .Branch }}-{{ checksum "package-lock.json" }}
+            - v{{ .Environment.CIRCLE_CACHE_VERSION }}-deps-master-{{ checksum "package-lock.json" }}
       - run:
           name: Install dependencies
           command: |
             npm install
-            npm dedupe
-            npm prune
-            npm install
       - run:
           name: List dependency versions
           command: |
@@ -47,7 +47,7 @@ jobs:
   test-jasmine:
     docker:
       # need '-browsers' version to test in real (xvfb-wrapped) browsers
-      - image: circleci/node:6.10.3-browsers
+      - image: circleci/node:8.9.4-browsers
     working_directory: ~/plotly.js
     steps:
       - checkout
@@ -82,7 +82,7 @@ jobs:
 
   test-syntax:
     docker:
-      - image: circleci/node:6.10.3
+      - image: circleci/node:8.9.4
     working_directory: ~/plotly.js
     steps:
       - checkout