Account for HttpExceptionInterface and headers.
Account for HttpExceptionInterface and headers.

Closes #201

sunshinephp/opencfp,MidwestPHP/opencfp_mwphp15,zymsys/opencfp,GrUSP/opencfp,phphants/opencfp,OpenWestConference/opencfp,sunshinephp/opencfp,localheinz/opencfp,PHPBenelux/opencfp,phphants/opencfp,monoku/opencfp,jugisahunk/200OK_CFP,DallasPHP/opencfp,pmeth/opencfp,zhenqing/opencfp,localheinz/opencfp,pmeth/opencfp,OpenWestConference/opencfp,DevOpsDaysChicago/opencfp,Acidburn0zzz/opencfp,monoku/opencfp,localheinz/opencfp,GrUSP/opencfp,DallasPHP/opencfp,MidwestPHP/opencfp_mwphp15,OpenWestConference/opencfp,jugisahunk/200OK_CFP,sunshinephp/opencfp,zhenqing/opencfp,phphants/opencfp,opencfp/opencfp,MidwestPHP/opencfp_mwphp15,OpenWestConference/opencfp,monoku/opencfp,MidwestPHP/opencfp_mwphp15,mdwheele/opencfp,brynary/opencfp,DevOpsDaysChicago/opencfp,brynary/opencfp,monoku/opencfp,pmeth/opencfp,PHPBenelux/opencfp,GrUSP/opencfp,mdwheele/opencfp,opencfp/opencfp,opencfp/opencfp,jugisahunk/200OK_CFP,Acidburn0zzz/opencfp,zymsys/opencfp,phphants/opencfp,DallasPHP/opencfp,PHPBenelux/opencfp,zhenqing/opencfp,GrUSP/opencfp,DevOpsDaysChicago/opencfp,localheinz/opencfp,brynary/opencfp,Acidburn0zzz/opencfp,mdwheele/opencfp,noahd1/opencfp,noahd1/opencfp,PHPBenelux/opencfp,noahd1/opencfp,zymsys/opencfp,mdwheele/opencfp