mentions: include mentioner in subject line.

The template looks like this:

Subject:

    #{creator_name} mentioned you in a comment on post ##{post_id}

Body:

    @#{creator_name} mentioned you in a \"comment\":/posts/#{post_id}#comment-#{id} on post ##{post_id}:

    [quote]
    #{DText.excerpt(body, "@"+user_name)}
    [/quote]

test/unit/comment_test.rb

@@ -57,7 +57,13 @@ class CommentTest < ActiveSupport::TestCase
           end
 
           dmail = Dmail.last
-          assert_equal("You were mentioned in a \"comment\":/posts/#{@comment.post_id}#comment-#{@comment.id}\n\n---\n\n[i]#{CurrentUser.name} said:[/i]\n\nHey @#{@user2.name} check this out!", dmail.body)
+          assert_equal(<<-EOS.strip_heredoc, dmail.body)
+            @#{CurrentUser.name} mentioned you in a \"comment\":/posts/#{@comment.post_id}#comment-#{@comment.id} on post ##{@comment.post_id}:
+
+            [quote]
+            Hey @#{@user2.name} check this out!
+            [/quote]
+          EOS
         end
       end
     end

test/unit/forum_post_test.rb

@@ -51,7 +51,13 @@ class ForumPostTest < ActiveSupport::TestCase
           end
 
           dmail = Dmail.last
-          assert_equal("You were mentioned in the forum topic \"#{@topic.title}\":/forum_topics/#{@topic.id}?page=1\n\n---\n\n[i]#{@user.name} said:[/i]\n\nHey @#{@user2.name} check this out!", dmail.body)
+          assert_equal(<<-EOS.strip_heredoc, dmail.body)
+            @#{CurrentUser.name} mentioned you in topic ##{@topic.id} (\"#{@topic.title}\":[/forum_topics/#{@topic.id}?page=1]):
+
+            [quote]
+            Hey @#{@user2.name} check this out!
+            [/quote]
+          EOS
         end
       end
     end