added server side time_to_live of session data

added server side time_to_live of session data, when the session_data is  expires the session gets reset.

first I thinking to implement it on application level, but I think the right place it the here (#7)

I know that invasive regarding adding a default timeout of 30 minutes but since the version is 0.0.4 I guess that is OK. security should start restrictive IMO.