* Moved zetacomponents/database to "suggest" in composer.json. If you rely on this feature you now need to include " zetacomponents/database" into "require" key in your own composer.json. (Issue #51)
* New method in Refresh grant called `rotateRefreshTokens()`. Pass in `true` to issue a new refresh token each time an access token is refreshed. This parameter needs to be set to true in order to request reduced scopes with the new access token. (Issue #47)
* Rename `key` column in oauth_scopes table to `scope` as `key` is a reserved SQL word. (Issue #45)
* The `scope` parameter is no longer required by default as per the RFC. (Issue #43)
* You can now set multiple default scopes by passing an array into `setDefaultScope()`. (Issue #42)
* The password and client credentials grants now allow for multiple sessions per user. (Issue #32)
* Scopes associated to authorization codes are not held in their own table (Issue #44)
**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