build: drop support node 5 and old

Scrum · Scrum · commit 368083e970ce · 2018-08-15T11:14:34.000+03:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,8 +5,6 @@ node_js:
   - v8
   - v7
   - v6
-  - v5
-  - v4
 
 after_success:
   - './node_modules/.bin/nyc report --reporter=text-lcov | ./node_modules/.bin/coveralls'
diff --git a/package.json b/package.json
@@ -13,7 +13,7 @@
   },
   "main": "lib/index.js",
   "engines": {
-    "node": ">=4"
+    "node": ">=6"
   },
   "scripts": {
     "prepush": "npm t",
