when using cache.save_hash, an `undefined` skin or cape hash means "do not touch"
while `null` means "overwrite as non-existent"
this was sent to redis after calling /capes/Notch for the first time:
"hmset" "notch" "c" "3f688e0e699b3d9fe448b5bb50a3a288f9c589762b3dae8308842122dcb81" "t" "1429651244222"
"hmset" "notch" "s" "a116e69a845e227f7ca1fdde8c357c8c821ebd4ba619382ea4a1f87d4ae94" "c" "" "t" "1429651244235"
as you can see, the first request stores the c(ape) but does not touch the s(kin), whereas the second request
sets the s(kin) and replaces the c(ape) value
- made sure that get_cape returns a status
- response.js returns 404 if body is empty
- 'X-Storage-Type: undefined' is no longer returned when status is `null`
