Added a filtering function to handle badly index arrays in certain mongo...

Passing in array data with broken sequential arrays created exceptions with $in, $nin, etc.
Added code which will re-index the query conditions array.

This can be re-created like so:

$arr['conditions']['id']['$in'] => array( 'a', 'b', 'c', 'd' );
unset( $arr['conditions']['id']['$in][2] ); // Break natural index order
$result = $this->Model->find( 'all', $arr );

Signed-off-by: Josh Rodarte <josh@hipstercreative.com>