[fix bug 1083381] Set twitter feed on homepage to not show @replies

Not quite ready to merge.

This change will mean Twitter @ replies will not be included in the cron job. One side effect of this is that the student ambassadors page will also not show replies in the timeline. If this is not desired (I'm getting confirmation in the bug), then I may need the guidance of either @pmclanahan or @jgmize on how best to accommodate this.