Merge branch 'fix-archive-link' into 'master'

Only display link to hyperkitty if archive is accessible to the user

Fixes #20 

See merge request !151
5 jobs for master in 2 minutes and 46 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #4271960
django-1.10

00:02:31

passed #4271958
django-1.8

00:02:24

passed #4271959
django-1.9

00:02:24

passed #4271962
allowed to fail
django-latest

00:01:36

passed #4271961
pep8

00:00:47