Update minimum version of djangocms-text-ckeditor for recent builds of django-cms

Using the previously recommended version of 2.0.5 results in `ImportError: No module named utils` since cms.plugins.utils has been removed.

Upgrading djangocms-text-ckeditor to 2.1.1 resolves this.

Signed-off-by: Martin Koistinen <mkoistinen@gmail.com>
Merge pull request #2609 from mkoistinen/update_dependencies

Inc. min. version of djangocms-text-ckeditor for recent builds of django-cms