Use CircleCI convenience image and sudo

sudo install latest npm

Author: hannahhenderson

.circleci/config.yml

@@ -3,13 +3,13 @@ jobs:
   build:
     working_directory: ~/mern-starter
     docker:
-      - image: node:7.9.0
+      - image: circleci/node:4.8.2
       - image: mongo:3.4.4
     steps:
       - checkout
       - run:
           name: update-npm
-          command: 'npm install -g npm@latest'
+          command: 'sudo npm install -g npm@latest'
       - restore_cache:
           key: dependency-cache-{{ checksum "package.json" }}
       - run: