Switch back from yarn to npm

.circleci/config.yml

@@ -7,11 +7,11 @@ jobs:
     steps:
       - checkout
       - restore_cache:
-          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "yarn.lock" }}
+          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "package-lock.json" }}
       - restore_cache:
-          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "src/yarn.lock" }}
+          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "src/package-lock.json" }}
       - run: apt-get update && apt-get -y install --no-install-recommends jq icnsutils graphicsmagick tzdata
-      - run: yarn
+      - run: npm install
       - run: npm run build
       - run: npm run package:windows
       - run: jq '.mac.target=["zip"]' electron-builder.json > /tmp/electron-builder.json && cp /tmp/electron-builder.json .
@@ -21,13 +21,13 @@ jobs:
       - run: sh -x ./scripts/cp_artifacts.sh release /tmp/artifacts
       - run: npm run lint:js
       - save_cache:
-          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "yarn.lock" }}
+          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "package-lock.json" }}
           paths:
             - "node_modules"
             - "~/.cache/electron"
             - "~/.cache/electron-builder"
       - save_cache:
-          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "src/yarn.lock" }}
+          key: npm-{{ arch }}-{{ .Branch }}-{{ checksum "src/package-lock.json" }}
           paths:
             - "src/node_modules"
       - store_artifacts:
@@ -45,7 +45,7 @@ jobs:
     steps:
       - checkout
       - run: apt-get update && apt-get -y install --no-install-recommends libgconf-2-4
-      - run: yarn
+      - run: npm install
       # https://github.com/SeleniumHQ/docker-selenium/issues/222#issuecomment-221307583
       - run: DBUS_SESSION_BUS_ADDRESS=/dev/null xvfb-run npm test
       - run: mkdir -p /tmp/test-results

.gitignore

@@ -9,8 +9,6 @@ npm-debug.log*
 
 build/
 dist/
-package-lock.json
-src/package-lock.json
 
 test-results.xml
 test_config.json

docs/development.md

@@ -6,14 +6,13 @@
 - C++ environment which supports C++11 (e.g. VS 2015, Xcode, GCC)
 - Python 2.7
 - Node.js 8.2.0 or later
-- Yarn
 - Git
 
 ### Installing dependencies
 After installation, dependencies of `src/` directory are also installed.
 
 ```
-$ yarn
+$ npm install
 ```
 
 ### Building