Allow optional NextState getTarget() model input

Since the NextState does not rely on the model to return the target, this will make the method consistent with functionality before the NextStateOr class was introduced.
Added a branch alias to composer.json
Merge pull request #8 from wcluijt/patch-2

Added a branch alias to composer.json
Merge pull request #7 from wcluijt/patch-1

Allow optional NextState getTarget() model input
run test with SF 2.3 and 2.4
Mark Doctrine as a hard dependency

In a Propel-backed project, there's no way of using the bundle. So, why not require Doctrine explicitly?
Added doctrine/orm base dependency, removed doctrine/common
Merge pull request #10 from kix/patch-1

Mark Doctrine as a hard dependency
Fix parameter
Add violations and new event when user has not the roles to reach the step
Added stillmaintained status
removed todo and unused use statment