Remove yield, ember appends application template to body element.
Update ember-rails
Upgrade to ember-1.0.0-pre.4 and clean up unused assets

Squashed commit of the following:

commit 413dc6ae2e62c6e7ea99777c73d8ec471de77b3f
Author: Patrick Baselier <patrick@kabisa.nl>
Date:   Sun Jan 20 10:05:38 2013 +0100

    Use assets from ember-rails and ember-1.0.0-pre.4

commit 0e0e773a3830b8448b81867c17e517daf1953c1a
Author: Patrick Baselier <patrick@kabisa.nl>
Date:   Sun Jan 20 10:04:51 2013 +0100

    Use latest ember-rails

commit 1219ce3cc4bdd0070077cd17bdea90fda1c191ce
Author: Patrick Baselier <patrick@kabisa.nl>
Date:   Sat Jan 19 11:56:29 2013 +0100

    Update ember-(data).js. Breaks stuff however...