I was going to open new issue for adding 'value', but looking at the parsing code I see why I didn't add one.  The way the new parser works it really wants to know the actual structure of the value, it doesn't have a good way to treat it as generic.  We could still add 'value' and just set it to the appropriate value, but there isn't currently a way to parse an unknown MIME header.

I think maybe I'll postpone this 'value' idea until we have a bit more experience with the API.