feat: require Node.js >=8.15

BREAKING CHANGE: Require Node.js => 8.15

Author: pvdlg

.travis.yml

@@ -3,7 +3,7 @@ language: node_js
 node_js:
   - 12
   - 10
-  - 8.3
+  - 8.15
 
 # Trigger a push build on release and greenkeeper branches + PRs build on every branches
 # Avoid double build on PRs (See https://github.com/travis-ci/travis-ci/issues/1147)

package.json

@@ -28,7 +28,7 @@
     "xo": "^0.25.0"
   },
   "engines": {
-    "node": ">=8.3"
+    "node": ">=8.15"
   },
   "files": [
     "lib",