Added yarn.

.travis.yml

@@ -1,4 +1,15 @@
 language: node_js
+before_install:
+  # Repo for Yarn
+  - sudo apt-key adv --keyserver pgp.mit.edu --recv D101F7899D41F3C3
+  - echo "deb http://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
+  - sudo apt-get update -qq
+  - sudo apt-get install -y -qq yarn
+install:
+  - yarn install
+cache:
+  directories:
+  - $HOME/.yarn-cache
 node_js:
   - "6"
   - "5"

appveyor.yml

@@ -11,7 +11,12 @@ install:
   # Get the latest stable version of Node.js or io.js
   - ps: Install-Product node $env:nodejs_version
   # install modules
-  - npm install
+  - choco install yarn
+  - refreshenv
+  - yarn install
+
+cache:
+  - "%LOCALAPPDATA%/Yarn"
 
 # Post-install test scripts.
 test_script:

tools/.yarnclean

@@ -0,0 +1 @@
+!browser-sync-ui/lib/plugins/history # need this for now because of https://github.com/yarnpkg/yarn/issues/1396#issuecomment-255965666