Update Travis CI config to work with the current supported Node.js versions

Author: petamoriken

.travis.yml

@@ -4,17 +4,17 @@ matrix:
     - os: linux
       dist: trusty
       sudo: required
-      node_js: "8" # to be removed on "December 2019"
+      node_js: "12" # to be removed on "April 2022"
     - os: osx
-      node_js: "8" # to be removed on "December 2019"
+      node_js: "14" # to be removed on "April 2023"
     - os: linux
       dist: trusty
       sudo: required
-      node_js: "10" # to be removed on "April 2021"
+      node_js: "14" # to be removed on "April 2023"
     - os: linux
       dist: trusty
       sudo: required
-      node_js: "12" # to be removed on "April 2022"
+      node_js: "16" # to be removed on "April 2024"
 addons:
   chrome: stable
   firefox: latest