#2753 - status_tag supports boolean status (fix)

Hi guys,

I fixed this issue little bit. Previous version didn't worked for me. It had been accepting only boolean value in a string which I think made no sense.
Because status_tag HTML classes are also generated from status string by `status_to_class` (which I personally thing is not very clear solution), it can happen that boolean status_tag will always have either 'yes' or 'no' classes. In my app I wanted to make this status_tag styled as 'ok', but it was always overriden by yes/no style. I changed the order of class definitions in CSS to preserve the priority.