Unset limit when page or page range is not specified

Fix #110 (backport of c627b01961dc40ec9e34123ca1065603e883783b in branch 2.2).

I'd like to do an app release today or tomorrow with Avocado and Serrano 2.1.  If 2.2 isn't going to be released for a while, then this backport would make the 2.1 branch usable for me.