What if instead of just coercing we validated it as well?

```@per_page.to_i``` must be >= 1

If it is < 1, then it has no affect on the query and neither does the page argument. Thus returning all results. The page number is only valid when there is a proper per_page limit.

When I put in a page number that doesn't make sense as a possible value say ```-1``` or ```boom``` kaminari just gives me page 1. So following that I would really want it to be ignored and fall back to a default value. Default value for ```@page``` is easy. Picking a default value for ```@per_page``` would be arbitrary.

Also, I wouldn't want to throw an exception because someone decided to put ```?per_page=boom``` in their address bar; I get enough email as it is.