examples: fix abort in nan version of 7_object_wrap

When creating a prototype method, the `FunctionTemplate` must be
attached to the `PrototypeTemplate`, not the resulting `Function`.

Fixes: #64
PR-URL: #70
Reviewed-By: Nicola Del Gobbo <nicoladelgobbo@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

Author: Gabriel Schulhof

7_factory_wrap/nan/myobject.cc

@@ -17,7 +17,7 @@ void MyObject::Init() {
   tpl->InstanceTemplate()->SetInternalFieldCount(1);
   // Prototype
   tpl->PrototypeTemplate()->Set(Nan::New("plusOne").ToLocalChecked(),
-      Nan::New<v8::FunctionTemplate>(PlusOne)->GetFunction());
+      Nan::New<v8::FunctionTemplate>(PlusOne));
 
   constructor.Reset(tpl->GetFunction());
 }