bug 839214 - live indexing to elastic search

(Sorry for the trailing commit. Leaving things separate to more easily view the diffs)

You'll need to fetch [my kuma-lib repos](https://github.com/groovecoder/kuma-lib), which means [the leeroy/mdn-github jenkins build](https://ci.mozilla.org/job/mdn-github/) is going to fail.

1. `git submodule update --init --recursive`
2. `vagrant provision`
3. Run tests. Make sure to include the 'search' app.

To spot-check, make sure you're running `./manage.py celeryd`, then:

1. update a doc in the site UI
2. go to https://developer-local.allizom.org/elastic/_plugin/head/ 
3. connect it to https://developer-local.allizom.org/elastic/
4. go to the 'Browser' tab and make sure there's a record in the `mdn-main_index` for the doc