Remove elasticsearch

[vossisboss]

No description provided.

[gasman]

Thanks @vossisboss! I think there are a few other references to elasticsearch we can remove now too:

• requirements/production.txt - looks like some of the boto / AWS stuff could possibly go too, but it's probably a deeper task to untangle all of that...
• search/views.py - currently there are two different code paths depending on whether Elasticsearch is in use or not, but the simple Page.objects.live().search version should work in all cases now. There's also a note about this in the readme, which can be dropped too if that does indeed work.
• settings/production.py - a bunch of Elasticsearch config that's no longer needed (and also a brief reference to it in settings/base.py that can also go)

[gasman]

All working nicely, so I'll go ahead and merge - the other bits of cleanup can be done as a follow-up.