Remove warning, fix double free, bump version

[mattsta]

Four tiny fixes here:

• remove a compile-time warning so we don't see it when building Redis
• fix a double free (on error conditions)
• refactor version checking to allow future versions to work too
• bump version for easier inclusion in other projects

[antirez]

Thank you Matt :+1: , merged.

Please if you find more time to take care of lua-cmsgpack, try to look at #16. Thanks!

[mattsta]

Thanks! I'll see what I can do about #16 now that I'm stuck in Lua mode for a while.