Hazaar\DBI\Table::where() and Hazaar\DBI\Table::find() update to allow string where clauses

Currently, the where() method requires that the argument be an array of standard search criteria. I think it would be nice to be able to use a standard SQL where clause instead.

Such as:

$db = new \Hazaar\DBI\Adapter();

$result = $db->users->where('group_id = 1234');