Update minimal node engine from 0.10 to 4. Just like with chai.

Author: JrSchild

package.json

@@ -1,6 +1,6 @@
 {
   "name": "chai-json-schema",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "Chai plugin for JSON Schema v4",
   "author": {
     "name": "Bart van der Schoor",
@@ -31,7 +31,7 @@
   },
   "main": "./index",
   "engines": {
-    "node": ">= 0.10"
+    "node": ">= 4"
   },
   "scripts": {
     "test": "grunt test"