Allow focusing at the end of a fragment

[Patrick Marchand]

When elements inserted / morphed into the dom are bigger than the screen, data-focus will focus on the center of the element. In some cases this is undesired. data-focus.end="" would allow us to force the focus to show the end of the element instead.

[Delaney]

try out issues-33 branch and see if the /examples/scroll_into_view example matches your needs