Fix deprecation warnings for Django 1.11 and Django 2.0.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/documents/views/document_views.py

@@ -4,9 +4,9 @@ import logging
 
 from django.contrib import messages
 from django.core.exceptions import PermissionDenied
-from django.core.urlresolvers import reverse, reverse_lazy
 from django.http import HttpResponseRedirect
 from django.shortcuts import get_object_or_404
+from django.urls import reverse, reverse_lazy
 from django.utils.encoding import force_text
 from django.utils.http import urlencode
 from django.utils.translation import ugettext_lazy as _, ungettext