drop support for node < 8

.travis.yml

@@ -1,18 +1,14 @@
 language: node_js
 
 node_js:
-  - stable
+  - 12
-  - v4
+  - 11
-  - v5
+  - 10
-  - v6
+  - 8
-  - v7
 
 sudo: false
 
-cache:
+cache: npm
-  yarn: true
-  directories:
-    - node_modules
 
 env:
   global:

index.js

@@ -1,5 +1,3 @@
-'use strict'
-
 /**
  * Exports
  */

package.json

@@ -26,7 +26,7 @@
     "date"
   ],
   "engines": {
-    "node": ">=4"
+    "node": ">=8"
   },
   "devDependencies": {
     "chai": "^4.2.0",

test.js

@@ -1,5 +1,3 @@
-'use strict'
-
 /* globals describe, it */
 
 const chai = require('chai')