Add fetch_title parameter to `fetch_article` method

So the `:page_title` `content_for` block isn't set if we don't want it (default is true)
Set `content_for` block manually in course_instance
Merge pull request #230 from theodi/bugfix-fix-course-instance-title

Fix Course Instance title
Merge branch 'refs/heads/master' into feature-slimmer