update circleci config, replace yarn with npm

.circleci/config.yml

@@ -7,35 +7,26 @@ version: 2
 jobs:
   build:
     docker:
-      # specify the version you desire here
       - image: circleci/node:8-browsers
 
-      # Specify service dependencies here if necessary
-      # CircleCI maintains a library of pre-built images
-      # documented at https://circleci.com/docs/2.0/circleci-images/
-      # - image: circleci/mongo:3.4.4
-
     working_directory: ~/repo
 
     steps:
       - checkout
 
-      # Download and cache dependencies
+      - run: sudo npm install -g npm@latest
+
       - restore_cache:
-          keys:
-          - v1-dependencies-{{ checksum "package.json" }}
-          # fallback to using the latest cache if no exact match is found
-          - v1-dependencies-
+          key: dependency-cache-{{ checksum "package.json" }}
 
-      - run: yarn install
+      - run: npm install
 
       - save_cache:
           paths:
             - node_modules
-          key: v1-dependencies-{{ checksum "package.json" }}
+          key: dependency-cache-{{ checksum "package.json" }}
 
-      # run tests!
-      - run: yarn test
+      - run: npm test
 
       - run: ./node_modules/.bin/codecov