bump to Rails 4
bump to Rails 4

wvengen/activeadmin-sortable-tree,zorab47/activeadmin-sortable-tree,zorab47/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,tripledub/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,NHSChoices/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,hotvulcan/activeadmin-sortable-tree,hotvulcan/activeadmin-sortable-tree,hotvulcan/activeadmin-sortable-tree,zorab47/activeadmin-sortable-tree