Merge pull request #11 from jdb8/fix-travis-build-update-yarn-node

Upgrade yarn and node to fix build

.travis.yml

@@ -2,18 +2,27 @@ sudo: false
 language: python
 python:
     - "3.5"
+
 install:
-    - nvm install 6
-before_install: yarn global add greenkeeper-lockfile@1
+    - nvm install 8
+
+before_install:
+  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.1.0
+  - export PATH="$HOME/.yarn/bin:$PATH"
+  - yarn global add greenkeeper-lockfile@1
+
 before_script: greenkeeper-lockfile-update
 after_script: greenkeeper-lockfile-upload
+
 env:
     global:
         - COVERALLS_SERVICE_NAME=travis-ci
         - COVERALLS_REPO_TOKEN=MUPeiBPH7d1yj7tt2yt3VNkkllD40Q9b3
+
 script:
     - make test
     - make coveralls
+
 deploy:
     provider: npm
     email: mark@larah.me