💚 🐛 yarn is preinstall in circle ci 2.0

circle.yml

@@ -6,21 +6,21 @@ jobs:
       - image: circleci/node:8.10.0
     steps:
       - checkout
-      - run:
-          name: install-yarn
-          command: 'sudo npm install -g yarn'
       - restore_cache:
-          key: dependency-cache-{{ checksum "package.json" }}
+          name: Restore Yarn Package Cache
+          keys:
+            - yarn-packages-{{ checksum "yarn.lock" }}
       - run:
-          name: install-yarn-wee
-          command: yarn
-      - run:
-          name: install-flow-typed-wee
-          command: yarn run flow-typed install
+          name: Install Dependencies
+          command: yarn install
       - save_cache:
-          key: dependency-cache-{{ checksum "package.json" }}
+          name: Save Yarn Package Cache
+          key: yarn-packages-{{ checksum "yarn.lock" }}
           paths:
-            - ./node_modules
+            - ~/.cache/yarn
+      - run:
+          name: Install flow-typed
+          command: yarn run flow-typed install
       - run:
           name: test
           command: yarn test