Reloadable attribute. Need a patch review.

Sometimes I need to reload some object from database, but I do not
always need to reload every attribute. If I know what attribute I need
to reload it would be great to do it, without performing huge select.

This patch is implementing this feature. It adds methods to AR::Base,
equal to attribute names, but ending with exclamation mark. Such
methods do reload attribute from database, but instead of:

select * from table_name;

it does

select field from table_name;

So, I can use @post.title, if I need to get a cached title, or I can
use @post.title!, if I need to fetch it directly from database.
— here is the ticket, i've opened for this feature. You can find a
patch there.