getRequest returns Request_String instead of Request a

[igstan]

What's the reason for not having getRequest and postRequest return Request a, i.e.:

getRequest :: BufferType a => String -> Request a
postRequest :: BufferType a => String -> Request a

If they were like this, it would be much easier to tell the library to use (Lazy) ByteStrings instead of Strings. The simplest way I could do that with what's in the library at this point is this:

request :: URI -> IO ByteString
request url = simpleHTTP (defaultGETRequest_ url) >>= getResponseBody

While it's not necessarily ugly or bad, I think it would be much nicer to have polymorphic getRequest/postRequest functions.