Add queryset_iterator

Since Django normally loads all objects into it's memory when iterating
over a queryset (even with .iterator, although in that case it's not
Django holding it in it's memory, but your database client) I needed a
solution that chunks the querysets so they're only keeping a small
subset in memory.
Update ChangeLog.rst for queryset iterator
Initial request package
Add a simple docstring to package
Initial http.request module
Add build_absolute_url
Upadate ChangeLog.rst for build_absolute_url