test: add node.js 12 in the test matrix

See https://github.com/nodejs/Release

Author: darrachequesne

.travis.yml

@@ -1,13 +1,14 @@
 language: node_js
 sudo: false
 node_js:
-  - '8'
-  - '10'
+  - "8"
+  - "10"
+  - "12"
 git:
   depth: 1
 matrix:
   include:
-    - node_js: node
+    - node_js: "12"
       env: BROWSERS=1
 cache:
   directories:

package.json

@@ -40,5 +40,8 @@
   "files": [
     "lib/"
   ],
-  "browser": "./lib/browser.js"
+  "browser": "./lib/browser.js",
+  "engines": {
+    "node": ">=8.0.0"
+  }
 }