[Bug] hdel returning nil unexpectedly

Potential bug. Correct me if I'm wrong, but shouldn't the `hdel` methods in the spec tests return 1 as per the redis spec (see http://redis.io/commands/hdel)? I was wondering why my specs were failing, while running the code in the console was working as intended. 

I was able to reproduce the error in the `hashes_spec.rb` file. (this fails the spec tests)

For some reason, when you delete a key from a hash with 2 or more keys, `hdel` returns nil.