build.sh: Bump DATE to 20140911

This pulls in my proxy-maintained flask-cors [1,2].

[1]: https://bugs.gentoo.org/show_bug.cgi?id=517478
     Summary: dev-python/flask-cors - A Flask extension adding a
       decorator for CORS support
     Ian Delaney (idella4) added my ebuild to the Portage tree [2].
[2]: http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/dev-python/flask-cors/
     Summary: ebuild written by W. T. King, from his overlay
     Date: 2014-09-09 02:56:48Z
docker-registry/Dockerfile.template: Drop Layman from the stack

I needed Layman in afa78a6e (docker-registry/Dockerfile.template: Add
flask-cors dependency, 2014-08-30), because my flask-cors ebuild
wasn't in the main Portage tree yet.  With 01d1a28f (build.sh: Bump
DATE to 20140911, 2014-09-12), we're pulling in a Portage tree that
does have my flask-cors package, so we no longer need the Layman stuff
here.