multi-line conditional and add --production flag

Author: kylemh

.travis.yml

@@ -11,7 +11,11 @@ before_install:
   - yarn global add greenkeeper-lockfile@2
 
 install:
-  - if [[ $TRAVIS_BRANCH == greenkeeper* ]]; then yarn install --silent; else yarn --pure-lockfile --silent; fi
+  - if [[ $TRAVIS_BRANCH == greenkeeper* ]]; then 
+      yarn install --silent; 
+    else
+      yarn --silent --pure-lockfile --production=true;
+    fi
 
 before_script:
   - greenkeeper-lockfile-update