Kaminari and will_paginate collision

I tried to integrate this gem to existing project that historically uses `will_paginate`. It turns out `will_paginate` takes precedence over `kaminari`. See the issue https://github.com/amatsuda/kaminari/issues/162. I took a look at both. Long story short `kaminari` appends class method `page` to every class inherited from AR::B, whereas `will_paginate` pollutes Relation, Association. I think there should be way not to pollute the whole AR but instead use a technique proposed in comments there. Also I think we don't need this line `require kaminari` because it injects the code to AR::B and user's applications may use different gem, instead I suggest inject `kaminari` stuff to `Feeder::Item` manually. WDYT?
Yes it does. But since `will_paginate` pollutes `Relation` then for example in this case:
```
Feeder::Item.order(:created_at).page(1).per(2)
```
`page` method will be called for `will_paginate` and you'll see exception `NoMethodError` for `per`. 
But in this case it will work as expected:
```
Feeder::Item.page(1).per(2)
```
So I'd suggest using `kaminari_page` rather then `page` all in all ;)