Update ez_setup.py to latest version.

ez_setup.py was retrieved from
https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py.

Reviewed at https://reviews.reviewboard.org/r/4617/.
Fix adminmedia templatetags (djblets).

The old "admin_media_prefix" tag is deprecated in favor of just using the
staticfiles framework with an "admin" prefix. This change fixes up djblets to
handle that.

Testing done: Viewed all of the changed pages.
Reviewed at https://reviews.reviewboard.org/r/4628/