chore(): update engines to match angular (#1504)

Updates the `engines` section in the `package.json` to match the one from Angular.

Fixes #1502.

Author: crisbeto

package.json

@@ -20,7 +20,7 @@
   "version": "2.0.0-alpha.9-3",
   "license": "MIT",
   "engines": {
-    "node": ">= 4.2.1 < 5"
+    "node": ">= 5.4.1 < 7"
   },
   "dependencies": {
     "@angular/common": "^2.0.0",