fix(regexp): properly construct new BSONRegExp when constructor called without new

Author: edaniels

lib/bson/regexp.js

@@ -14,7 +14,7 @@ function alphabetize(str) {
  * @return {BSONRegExp} A MinKey instance
  */
 function BSONRegExp(pattern, options) {
-  if (!(this instanceof BSONRegExp)) return new BSONRegExp();
+  if (!(this instanceof BSONRegExp)) return new BSONRegExp(pattern, options);
 
   // Execute
   this._bsontype = 'BSONRegExp';