Pass configuration settings to the class in the form of
key/value pairs. As a shortcut, if the second argument
is omitted and the key is a string, the setting is
assumed to be the DSN string used by PDO to connect
to the database (often, this will be the only configuration
required to use Idiorm). If you have more than one setting
you wish to configure, another shortcut is to pass an array
of settings (and omit the second argument).