lua port of PHP's unserialize function. Based off of:

https://gist.github.com/cristobal/3647759

Which in turn is based off of phpjs's implementation of unserialize:

http://phpjs.org/functions/unserialize

Does not currently support custom object encodings, but should work with pretty 
much any other kind of data.

Note that references are treated as regular integers.

You can find a handy description of php's serialization format at:

https://evertpot.com/133/