Fix httplib endheaders if a message_body exists
Fix httplib endheaders if a message_body exists

Fixes #140

poussik/vcrpy,yarikoptic/vcrpy,aclevy/vcrpy,kevin1024/vcrpy,mgeisler/vcrpy,graingert/vcrpy,agriffis/vcrpy,ByteInternet/vcrpy,poussik/vcrpy,gwillem/vcrpy,bcen/vcrpy,graingert/vcrpy,kevin1024/vcrpy,ByteInternet/vcrpy,IvanMalison/vcrpy