Include groups in Node ACL if specified in workflow configuration. Fixes #278

Here is my workflow confguration:

<state name="public" callback="leanneodea.workflow.workflow_callback">

      <key name="title" value="_(u'Public')" />
      <key name="order" value="2" />

      <key name="inherit" value="0" />
      <key name="system.Everyone" value="view" />
      <key name="role:viewer" value="view" />
      <key name="role:editor" value="view add edit state_change" />
      <key name="role:owner" value="view add edit manage state_change" />
      <key name="group:publisher" value="view add edit state_change" />
</state>


I want users in a publisher group to only be able to view and publish content, currently there is no way of easily doing so that I can see.  The group:publisher key is being ignored. Fix attached.