Guess file extension based on content-type. When downloading a file, and no path is supplied to store it, guess the file extension using mimetypes and the content-type header. Also supply a unit test for the HotLinkImageForm.

.user_photo {
   margin: 1em;
   display: inline-block;
}
.owner_photo {
   border: 1px solid gray;
}
.owner_photo img {
   margin: auto;
   width: 100%;
}
hr.footer_divider {
   margin-top: 1.5em;
}