Add yarn.lock, update CI services to run yarn

.gitignore

@@ -1,5 +1,7 @@
 node_modules/
-npm-debug.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
 package-lock.json
 
 .nyc_output/

.travis.yml

@@ -10,12 +10,17 @@ matrix:
     - node_js: 8 # Version used to deploy to npm registry
       env: BUILD_ENV=production
 
-cache:
-  directories:
-    - ~/.npm
+cache: yarn
+
+before_install:
+  - yarn global add greenkeeper-lockfile@1
 
 before_script:
-  - NODE_ENV=$BUILD_ENV npm run build
+  - greenkeeper-lockfile-update
+  - NODE_ENV=$BUILD_ENV yarn build
+
+after_script:
+  - greenkeeper-lockfile-upload
 
 notifications:
   email:
@@ -49,5 +54,5 @@ deploy:
 # If the current release is a stable release, remove potential pre-release tag
 after_deploy: |
   if [ "$(npm_dist_tag)" == "latest" ]; then
-    npm dist-tag rm thelounge next || true
+    yarn tag remove thelounge next || true
   fi

appveyor.yml

@@ -15,19 +15,19 @@ environment:
 
 install:
   - ps: Install-Product node $env:nodejs_version
-  - appveyor-retry npm install
-  - npm run build
-  - npm install mocha-appveyor-reporter
+  - yarn --frozen-lockfile
+  - yarn build
+  - yarn add mocha-appveyor-reporter
   - echo --reporter mocha-appveyor-reporter >> test/mocha.opts
 
 test_script:
   - node --version
-  - npm --version
-  - npm test
+  - yarn --version
+  - yarn test
 
 # cache npm modules
 cache:
-  - '%AppData%\npm-cache -> package.json'
+  - "%LOCALAPPDATA%\\Yarn"
 
 # Don't actually build
 build: off