Digg-style pagination, and retain GET params
This snipplet is based on [Ryan Kanno's work](http://blog.localkinegrinds.com/2007/09/06/digg-style-pagination-in-django/) and [snipplet #2680](http://djangosnippets.org/snippets/2680/). The page numbers are basically composed by `pages_outside_trailing_range`, `page_range` and `pages_outside_leading_range`. The GET params in the request(except for `page` itself) are retained across different pages. This is important when you have an `order_by` param working inline.
- pagination