preserve Accept header for 303 redirects

Hello,

It would be great to preserve the Accept header when doing a 303 redirect.  This is the behavior of the clients curl and wget and the dx.doi.org server  (see <https://github.com/kraih/mojo/issues/524>).

Also, section 4.3 of <http://www.w3.org/TR/cooluris/> describes this further.

thanks
Brian