Require Node.js 6 or newer

Author: realityking

.travis.yml

@@ -1,6 +1,5 @@
 language: node_js
 node_js:
-  - 4
   - 6
   - 8
   - 'stable'

package.json

@@ -4,7 +4,7 @@
   "description": "Parse curl --trace option output to raw HTTP message",
   "main": "lib/parser.js",
   "engines": {
-    "node": ">= 4"
+    "node": ">= 6"
   },
   "scripts": {
     "test": "scripts/test",