add devise for authentication
add devise to gemfile
new navigation for admins
routes, controllers and model for admins
controller for admin interface
views for admin interface
add method to site model for admin interface
admin css, js, helpers and tests
edit admin users
Merge branch 'master' into admin_interface
create dashboard
admin preview for unpublished sites
route for preview
possibility to edit own user data
some gems for admin interface
create admin from scratch
correct typo
add seeds to readme
add possibility to view and delete site comments
new order for admin sites overview