Retrieve title from table of contents

Depends on PR https://github.com/zetacomponents/Document/pull/3
Add check whether visitor exists

To prevent the code from breaking due to missing functionality in ZetaComponents (https://github.com/zetacomponents/Document/pull/3) we have added a check that we consult the table of contents
only when the visitor is set
Update ezcDocument to the latest version

We have submitted 2 pull requests to ezcDocument in order
to allow a Role to return the calling visitor and more.
Kore Nordmann merged this PR and tagged a new release, so we
can now include it.
Merge branch 'scrybe-plugin' into develop