Update Hal Plugin to support entities with $id = 0

Update Hal Plugin to support entities with $id = 0, these were currently not rendered because of a wrong if-clause
Update Hal Plugin to embed entities with $id = 0

Antoher change related to issue https://github.com/zfcampus/zf-hal/issues/44 .
The entity with `$id = 0` was also not properly embedded in the collection because of another similar faulty if clause, this time in the `extractCollection` method. This change fixes the issue and makes sure that the entity is properly rendered.
Merge branch 'hotfix/47'

Close #47
Merge pull request #45 from Wilt/develop

Update Hal Plugin to support entities with $id = 0
Merge branch 'hotfix/45' into develop

Forward port #45