Replace login_required decorator with a validating one

This one will validate that the url is under /accounts/, which is
the only part we are going to be excluding from caching once we
move the website to https-only.

pgweb/docs/views.py

@@ -2,7 +2,7 @@ from django.shortcuts import render_to_response, get_object_or_404
 from django.http import HttpResponseRedirect, HttpResponsePermanentRedirect
 from django.http import Http404
 from django.template.context import RequestContext
-from django.contrib.auth.decorators import login_required
+from pgweb.util.decorators import login_required
 from django.db.models import Q
 from django.conf import settings