session_save correction

[btouchard]

on session_save function, you try to access to $client->u_k variable definition, but $client is not passed on function argument... So pass a client in argument, or replace $client by $this without this, coun't save session ;)

but noce work, thank ;)

benjamin

[smartinm]

Thanks for catch this issue.

The session_save function must be static and receive $client by parameter.

Fixed bug and README example.