add greenkeeper-lockfile

Author: vinaypuppal

.travis.yml

@@ -6,6 +6,9 @@ node_js:
 before_install:
   - 'curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 0.27.5'
   - 'export PATH="$HOME/.yarn/bin:$PATH"'
+  - yarn global add greenkeeper-lockfile@1
+before_script: greenkeeper-lockfile-update
+after_script: greenkeeper-lockfile-upload
 cache: yarn
 env:
   global: