Removed gratuitous paragraph

Namespaces are handled by composer; also registerNamespaces() is not available in symfony 2.1 any more
Fixed Doctrine\Common\Annotations\AnnotationException

The error was:
  [Semantical Error] The annotation "@Doctrine\ORM\Mapping\generatedValue" in property Acme\Message  
  Bundle\Entity\Message::$id does not exist, or could not be auto-loaded.
Merge pull request #158 from fogs/master

Documentation fixes