fix breadcrumb styling in safari

fixes: CNVS-15931

this also fixes some logic in newfiles, it was
ellipsising only the last crumb. it is supposed
to ellipsize all the crumbs between "Files > "
and the last crumb, not the last crumb.

test plan:
open newfiles in safari, make sure the crumbs don't
look like http://screencast.com/t/KYo8xga1YbQ0

make sure the crumbs in the middle ellipsize
and the last crumb is allowed to be 500px

Change-Id: I70c42c4f1f1cd1872c72e9260739867ca493892b
Reviewed-on: https://gerrit.instructure.com/42221
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Product-Review: Ryan Shaw <ryan@instructure.com>