Unwind and allow non-string values

[victorquinn]

See this for more details on current implementation.

Turns out, we can use the Memcached flags in order to implement the "what gets put in gets pulled out" functionality. This may not be entirely compatible with another library as they could use the flags for something different, but it seems this is the most ideal solution.

I will evaluate other libraries and see if there is some consensus as to the value of these flags to indicate type.

This is not entirely a prerequisite for implementing incr/decr but generally needed and a good idea.