fixed; add EventEmitter props to reserved paths

throw friendly errors when `emit` or `_events` are used in schema.

#1338

lib/schema.js

@@ -211,7 +211,7 @@ Schema.prototype.add = function add (obj, prefix) {
  *
  * Keys in this object are names that are rejected in schema declarations b/c they conflict with mongoose functionality. Using these key name will throw an error.
  *
- *      on, db, init, isNew, errors, schema, options, modelName, collection
+ *      on, emit, _events, db, init, isNew, errors, schema, options, modelName, collection, _pres, _posts
  *
  * _NOTE:_ Use of these terms as method names is permitted, but play at your own risk, as they may be existing mongoose document methods you are stomping on.
  *
@@ -229,8 +229,10 @@ reserved.errors =
 reserved.schema =
 reserved.options =
 reserved.modelName =
-reserved._pres = reserved._posts = // hooks.js
-reserved.collection = 1;
+reserved.collection =
+reserved.emit =    // EventEmitter
+reserved._events = // EventEmitter
+reserved._pres = reserved._posts = 1 // hooks.js
 
 /**
  * Gets/sets schema paths.