Update CircleCI config

Author: philipstanislaus

.circleci/config.yml

@@ -5,7 +5,23 @@ jobs:
       - image: circleci/node:10.11.0
     steps:
       - checkout
+
+      # Download and cache dependencies
+      - restore_cache:
+          keys:
+            - v1-dependencies-{{ checksum "package.json" }}
+            # fallback to using the latest cache if no exact match is found
+            - v1-dependencies-
+
+      - run: yarn install
+
+      - save_cache:
+          paths:
+            - node_modules
+          key: v1-dependencies-{{ checksum "package.json" }}
+
       - run: |
+          yarn
           yarn run lint
           yarn run build
           yarn run test-and-send-cov-to-coveralls