Use own copy of django.contrib.markups.templatetags.markups for future evolution and to avoid deprecation
refined _get_user_flagger()

Had a use case where COMMENT_FLAG_USER_ID was not set, and 'Zinnia-Flagger' user had already been created.  This fix prevents a the following error:

IntegrityError: duplicate key value violates unique constraint "auth_user_username_key"
DETAIL:  Key (username)=(Zinnia-Flagger) already exists.
Use Markdown v2.3.1
Pep8 on tests/views.py
Adapt zinnia.markups to the needs
Add documentation about zinnia.markups
Add tests when a markup library is not installed
Merge branch 'patch-1' of git://github.com/smcoll/django-blog-zinnia into smcoll-fix-user-flagger
Add tests for issue #245
Skip tests of Entry.html_content if some libraries are not installed
Specify versions used for markups libraries
Add advanced test for zinnia.markups
Merge branch 'markups'
Updating number of tests
Does not make distinction anymore if django_xmlrpc is not installed
Fix flags tests launched with the default django test runner