circleci: upgrading docker and silencing yarn

circle.yml

@@ -1,9 +1,12 @@
 ## Customize the test machine
 machine:
+  pre:
+    - curl -sSL https://s3.amazonaws.com/circle-downloads/install-circleci-docker.sh | bash -s -- 1.10.0
   post:
       - pip install --upgrade docker-compose==1.8.0
       - npm install -g triton yarn
       - echo '{"url":"https://eu-ams-1.api.joyent.com","account":"'$SDC_ACCOUNT'","keyId":"c3:30:35:9b:85:48:73:44:31:cc:4b:2e:6a:00:16:e2","name":"eu-ams-1","curr":true}' | triton profile create -f -
+      - alias yarn='yarn > /dev/null'
 
   timezone:
     Europe/London