\DateTime properties cannot be indexed

[Martin1982]

When running solr:index:populate on an entity with this field;

/**
 * @var \DateTime
 *
 * @Solr\Field(type="date")
 */
protected $publicationDateStart;

The following error occurs:

A error occurs: no declaration for document found in entity DateTime

[Martin1982]

I just noticed this is solved in issue #123 but having it in the README.md would help not to fall for it again ;)

[Martin1982]

While working on my index I came across another error from Solr complaining about the date format. In the end this was the solution that worked for me;

 * @Solr\Field(type="datetime", getter="format('Y-m-d\TH:i:s.z\Z')")

[floriansemm]

Thanks good point. Documentation is now update to date.