Quote values in DOM selectors for Nokogiri compatibility.

git-svn-id: http://svn.redmine.org/redmine/trunk@13619 e93f8b46-1217-0410-a6f0-8f06a7374b81
Replaced some #assert_tag with #assert_select.

git-svn-id: http://svn.redmine.org/redmine/trunk@13620 e93f8b46-1217-0410-a6f0-8f06a7374b81