feat(router): route deis.domain to controller

Forwards requests to deis.domain to the controller.

TESTING: rebuild the router and controller with this change:

    $ make -C router build restart
    $ make -C controller build restart

Test that deis.domain routes to the controller and that other
requests to the domain route to the app. Also, send several requests
to the API and be sure that nothing broke related to auth because
of the proxying of requests.

The integration tests were updated to test the controller and the app
routing, so you can also `cd test && bundle exec rake`.

Also, try creating an app with the name of 'deis' - it should be
rejected.

replaces #974
part of #535
test(controller): check for appname = deis
fix(router): restore check_cmd and grep nginx.conf

We were having issues with router coming up due to "<no value>"
being templated into /etc/nginx/nginx.conf. Thanks @gabrtv.
Merge pull request #1011 from deis/controller-behind-router

feat(router): route deis.domain to controller
docs(UPGRADING.md): add upgrade documentation

Adds documentation outlining two upgrade workflows for Deis clusters.

closes #1012
Merge pull request #1031 from deis/upgrading_deis

docs(UPGRADING.md): add upgrade documentation