code: function MongoCrud(uri, options, gridFS) {
      this.uri = uri || 'mongodb://localhost:27017/mongo-crud-test';
      this.options = options || {};
      this.gridFS = gridFS;
  }
docs: Creates a MongoCrudLayer instance with given properties.
  
  @param uri - the MongoDB URI, defaults to 'mongodb://localhost:27017/mongo-crud-test
  @param options - Options used when connecting to MongoDB, defaults to an empty object
  @param gridFS - set to true, if objects exceed MongoDB document limit of 16mb, to store
  objects with GridFS mechanism
  @constructor