Update CI to use Yarn

Author: trentmwillis

.travis.yml

@@ -5,11 +5,20 @@ node_js:
   - "4"
 
 cache:
+  yarn: true
   directories:
-    - node_modules
+    - $HOME/.npm
+    - $HOME/.cache
 
 before_install:
-  - if [[ `npm -v` != 3* ]]; then npm i -g npm@3; fi
-  - npm config set spin false
-  - npm install -g bower
+  # Since we override the install hooks, we need to setup Yarn on our own
+  - curl -o- -L https://yarnpkg.com/install.sh | bash
+  - export PATH=$HOME/.yarn/bin:$PATH
+  - yarn global add bower
   - bower --version
+
+install:
+  - yarn install --no-lockfile
+
+script:
+  - yarn test

appveyor.yml

@@ -15,20 +15,19 @@ init:
 # Install scripts. (runs after repo cloning)
 install:
   - ps: Install-Product node $env:nodejs_version $env:platform
-  - npm i -g npm@^3
-  - npm config set spin false
-  - npm install -g bower
-  - npm install
+  - yarn global add bower
+  - yarn install
 
 # Post-install test scripts.
 test_script:
   - node --version
-  - npm --version
+  - yarn --version
   - bower --version
-  - npm test
+  - yarn test
 
 cache:
   - '%APPDATA%\npm-cache'
+  - "%LOCALAPPDATA%\\Yarn"
 
 # Don't actually build.
 build: off