Add time to export filename (CTFd#1949)

* Add time to export filename

export.py

@@ -19,7 +19,7 @@
             shutil.copyfileobj(backup, target)
     else:
         ctf_name = config.ctf_name()
-        day = datetime.datetime.now().strftime("%Y-%m-%d")
+        day = datetime.datetime.now().strftime("%Y-%m-%d_%T")
         full_name = "{}.{}.zip".format(ctf_name, day)
 
         with open(full_name, "wb") as target: