**If you're upgrading from v1.0.8 there are lots of breaking changes**
* Rewrote the session storage interface from scratch so methods are more obvious
* Included a PDO driver which implements the storage interfaces so the library is more "get up and go"
* Further normalised the database structure so all sessions no longer contain infomation related to authorization grant (which may or may not be enabled)
* A session can have multiple associated access tokens
* Induvidual grants can have custom expire times for access tokens
* Authorization codes now have a TTL of 10 minutes by default (can be manually set)
* Refresh tokens now have a TTL of one week by default (can be manually set)
* The client credentials grant will no longer gives out refresh tokens as per the specification