fix order by

order by did not accept more than one layer of sorting at a time.  it now accepts ['column', 'desc'] for one layer ordering, or [['col', 'desc'], ['col2', 'desc']], or even ['col', 'desc', 'col2', 'desc'] for multi-level ordering.
Merge pull request #23 from kdavh/bug/fix-order-by

fix order by