WIP: Search for Community using elasticsearch

First cuts for search feature for Community
While we might still want to skip the cancancan authorization check, we need to take permissions into account.

Below, we're returning all posts that the search returns, which might include posts the user doesn't have permission to see. Dave and I see two options:

1. Filter `@records` below to all of the posts that the current user has permission to see (using `can? :read, record` or something similar).

2. Somehow include our notion of permissions in Elasticsearch so that it only returns posts that the user has permission to see.