Fixed scrolling by links in linear story viewer.
Fixed scrolling by links in linear story viewer.

For some reason, I was calculating the scroll using the header's offset,
which was changing (even though it's absolutely positioned, hmmm).  Just
using the outer height of the header works great.

denverfoundation/storybase,denverfoundation/storybase,denverfoundation/storybase,denverfoundation/storybase