set supported node engines

Author: pasupulaphani

package.json

@@ -8,7 +8,7 @@
     "url": "git+ssh://[email protected]/pasupulaphani/simple-redis-store.git"
   },
   "engines": {
-    "node": "*"
+    "node": ">=4"
   },
   "bugs": {
     "url": "https://github.com/pasupulaphani/simple-redis-store/issues"