Godeps/_workspace/src/gopkg.in/mgo.v2/session.go
func (c *Collection) RemoveId(id interface{}) error {
	return c.Remove(bson.D{{"_id", id}})
}
func (c *Collection) RemoveId(id interface{}) error {
	return c.Remove(bson.D{{"_id", id}})
}
// RemoveId is a convenience helper equivalent to:
//
//     err := collection.Remove(bson.M{"_id": id})
//
// See the Remove method for more details.