An outline view that can be scrolled without it having fits.
Factor -scrollRectToVisible: out into a function.
Correct the visibility of the outline view header.
Add the outline view to the umbrella header.

There doesn’t seem to be any specific style of organization to this, so
I’ve just added it at the end.
Merge pull request #135 from github/outline-view-without-scrolling-fits

An outline view that can be scrolled without it having fits.