Content advisory

Look at story 275 for an example story that has a content advisory.

I am not happy about the change to the styles (&:last-child to an explicit class) in the story header but I couldn't think of a simpler way to do it since the content advisory is not always present and should not be counted as a child for the purposes of this styling and there is no shared class/type on these elements. 

I'm also not sure if it makes sense to use the same full size modal rather than one that just fits the text.  It seems nice and simple to have all the modals look the same.