Allow className to be a function.
router.previousPath
Release 0.2.24
Set data-fallthrough="true" to ignore in app routing
Release 0.2.25
Close Models and Collections
Make sure relations aren’t overwritten without being closed.
Add setClosable/closeClosable API to ItemView

Any subviews can then be added with setClosable, and
they will be properly closed when the view is closed.
Make sure any existing children are closed when rerendered.
Add ctx.set, objects will be closed when route is left.

ctx.set can be used to set models and views while routing,
and they will be properly closed when the route is left.
Add canLeave to Router.

Adds ability to check whether we can route away from 
the current page. Function should return falsy if we can
not leave the page.
Add bindToWindow/unbindWindow to highbrow.BindTo.

Any events bound to the window when a view is rendered
must be properly detached when the view is closed. This
api lets that happen automatically.
When setting existing collection/model, no need to close it.
Release 0.3.0: Memory management improvements