Blog links in newsfeed open a modal for a consistent behavior

@ottman @markeharding this is suggestion coming out of @edgebal 's modal pager work.

The quick fix for blogs in modal pager is to just skip over them, but a more consistent experience would be to support opening them up in the modal.

I'll schedule this for a day's work of work to make the formatting just right, but I wanted to get your feedback on the proposal