Fix for links not disabling on maxdate

As far as my understanding of Django reahes as of now, this should work.
Hopefully fixes the rankings on successive pages
oops
FIX
This should be a working fix
Fix for pagenav

Fixes some links being active when they should not. Still need to fix
the for loop creating page links
Merge pull request #179 from hewoo/periodpagenav-fix

Periodpagenav fix