Add Node.js 12 to testing (#14)

coreyfarrell · sindresorhus · commit 574423495cf7 · 2019-04-27T17:59:54.000+07:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,4 +1,5 @@
 language: node_js
 node_js:
+  - '12'
   - '10'
   - '8'
