ci: fixes ENOSPC warnings (#2256)

Author: mxschmitt

.travis.yml

@@ -4,6 +4,10 @@ node_js:
 cache:
   - npm
   - yarn
+before_install:
+  # Fixes an issue where the max file watch count is exceeded, triggering ENOSPC
+  # https://stackoverflow.com/questions/22475849/node-js-error-enospc#32600959
+  - echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
 script:
   - yarn lint
   - yarn test