Add a note for creating the security.yml
Update creating_cms_using_cmf_and_sonata.rst
Update creating_cms_using_cmf_and_sonata.rst

Added linebreaks and changed the sentence to be more clear...
Update creating_cms_using_cmf_and_sonata.rst
Merge pull request #178 from chrootLogin/patch-1

Add a note for creating the security.yml