Added Last Updated Info to Bottom of Course Pages

![screen shot 2014-09-19 at 12 43 07 am](https://cloud.githubusercontent.com/assets/910510/4330834/9431afda-3fb7-11e4-84a6-9c91d4f6a125.png)

@rocha @dsjen 
I'm fine not testing private methods.  The one path not covered is when the forum feature is enabled.  The removed tests set `show_engagement_forum_activity` to `True` to make sure that forum data was returned.