make asserts count for have_tag

lib/webrat/core/matchers/have_tag.rb

@@ -57,14 +57,14 @@ module Webrat
     # the supplied tag with the associated selectors
     def assert_have_tag(name, attributes = {})
       ht = HaveTag.new([name, attributes])
-      raise Test::Unit::AssertionFailedError.new(ht.failure_message) unless ht.matches?(response_body)
+      assert ht.matches?(response_body), ht.failure_message
     end
     
     # Asserts that the body of the response
     # does not contain the supplied string or regepx
     def assert_have_no_tag(name, attributes = {})
       ht = HaveTag.new([name, attributes])
-      raise Test::Unit::AssertionFailedError.new(ht.negative_failure_message) if ht.matches?(response_body)
+      assert !ht.matches?(response_body), ht.negative_failure_message
     end
 
   end