Publish with CircleCI (#33)

Add CircleCI support for publishing to NPM when there's a new version tag.

.circleci/config.yml

@@ -3,19 +3,48 @@
 # Check https://circleci.com/docs/2.0/language-javascript/ for more details
 #
 version: 2
+
+defaults: &defaults
+  docker:
+    # specify the version you desire here
+    - image: circleci/node:lts
+
+    # 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
+
 jobs:
-  build:
-    docker:
-      # specify the version you desire here
-      - image: circleci/node:lts
+  test:
+    <<: *defaults
+    steps:
+      - checkout
 
-      # 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
+      # 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-
 
-    working_directory: ~/repo
+      - run: yarn install
 
+      - save_cache:
+          paths:
+            - node_modules
+          key: v1-dependencies-{{ checksum "package.json" }}
+
+      # run tests!
+      - run: yarn test:ci
+
+      - persist_to_workspace:
+          root: ~/repo
+          paths: .
+
+  build:
+    <<: *defaults
     steps:
       - checkout
 
@@ -35,3 +64,43 @@ jobs:
 
       # run tests!
       - run: yarn test:ci
+
+      # build
+      - run: yarn build
+
+      - persist_to_workspace:
+          root: ~/repo
+          paths: .
+
+  deploy:
+    <<: *defaults
+    steps:
+      - attach_workspace:
+          at: ~/repo
+      - run:
+          name: Authenticate with registry
+          command:
+            echo "//registry.npmjs.org/:_authToken=$npm_TOKEN" > ~/repo/.npmrc
+      - run:
+          name: Publish package
+          command: npm publish
+
+workflows:
+  version: 2
+  only_test:
+    jobs:
+      - test
+  test-deploy:
+    jobs:
+      - build:
+          filters:
+            tags:
+              only: /^v.*/
+      - deploy:
+          requires:
+            - build
+          filters:
+            tags:
+              only: /^v.*/
+            branches:
+              ignore: /.*/