Merge pull request #679 from mattermost/fix-file-content-type

Blank Content-Type for file GETs.

api/file.go

@@ -349,6 +349,7 @@ func getFile(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	w.Header().Set("Cache-Control", "max-age=2592000, public")
 	w.Header().Set("Content-Length", strconv.Itoa(len(f)))
+	w.Header().Set("Content-Type", "") // need to provide proper Content-Type in the future
 	w.Write(f)
 }