Cursor support and addHeader().

Not sure if addHeader() was the way to go, but I wanted to allow headers to work for now and didn't like the arrays. 

Seeing as a cursor does not contain the collection, I had to make it work slightly differently. I wondered about `withCursor()` but it was weird to send a collection and a cursor to a method called that, so I just decided to shove the cursor into the collection.

Because paginators are bigger and more complex, they get their own method.

Fun caviat for that one, the paginator will not ALWAYS have a collection, it will only ever do that if its the Laravel collection. Seeing as this is a Laravel only package, I feel confident to just assume that.