fix: bring min node version in line with still supported (#1374)

Author: kellyselden

README.md

@@ -26,7 +26,7 @@
   <a href="https://www.npmjs.com/package/chai">
     <img
       alt="node:?"
-      src="https://img.shields.io/badge/node-%3E=8.0-blue.svg?style=flat-square"
+      src="https://img.shields.io/badge/node-%3E=4.0-blue.svg?style=flat-square"
     />
   </a>
   <br/>

package.json

@@ -37,7 +37,7 @@
     "test": "make test"
   },
   "engines": {
-    "node": ">=8"
+    "node": ">=4"
   },
   "dependencies": {
     "assertion-error": "^1.1.0",