rejectedsoftware/vibe.d — pull request #884 by Extrawurst (2014-10-28 15:54:37+00:00)
Title: fix null reply for boolean results

since the documentation states about the reply that:
`OK if SET was executed correctly. Null reply: a Null Bulk Reply is returned if the SET operation was not performed becase the user specified the NX or XX option but the condition was not met.`

so an empty result is a false return see: http://redis.io/commands/set

this fixes issue #880