where x and y or a and b

Hey Tim, does this library expose any api for creating a statement like 

```
delete from `routes_rules` 
where `route_id` = 369 and `rule_id` = 84 or 
      `route_id` = 369 and `rule_id` = 86 or 
      `route_id` = 369 and `rule_id` = 103
```

?

Using `orWhere` makes all the ANDs ORs, and `where` + `andWhere` makes all the ORs ANDs.
