Removed Bitdeli badge.

Merge pull request #3 from bitdeli-chef/master

Add a Bitdeli badge to README

Updated screenshot URL.

Merge pull request #2 from bitinn/master

fix issue on insert query side-effect

one fix oversight

fix silly mistake on where query

do not use object id as session id, mongodb index can achieve similar lookup speed with a simple index on session_id field, with this change we completely avoid truncating md5 session id to 24 hex string, and we reduce the query needed in sess_update from 3 (get, delete, insert) to 1 (update)

a few bugfix: 1. update mongodbe last_activity in sess_update; 2. keep up with codeigniter 2.1.3 changes on sess_destroy; 3. do not affect mysql session id generation, substr when needed to generate mongodb objectID

Fixed _sess_gc() to purge all expired session. Thanks to @dthpto

Linked to the V2 branch of MongoDB active record library.

Fixed typo.

Fixed a major bug in sess_update() which cause improper document insetions, plus other minor improvements.

Updated README file.