Merge pull request #8 from ghindle/ordered-jobs-on-db

Enforce ordered popping of jobs off the database queue

src/WP_Queue/Connections/DatabaseConnection.php

@@ -68,7 +68,7 @@ public function pop() {
 			SELECT * FROM {$this->jobs_table}
 			WHERE reserved_at IS NULL
 			AND available_at <= %s
-			ORDER BY available_at
+			ORDER BY available_at, id
 			LIMIT 1
 		", $this->datetime() );