Switch to elasticsearch for search

The double-metaphone search implementation was rather slow for longer
queries, it is also rather brittle as it relies on the document being
indexed in a certain way for it to be searchable. Switching to
elasticsearch means that the indexing can be done by simply handing it
the whole document, and from some initial testing it seems to be
returning more relevant results than double metaphone in mongo.

Elasticsearch does support double metaphone, though I believe you need a
plugin, so we can always revisit this approach in the future if needed.
Remove duplicated logic in storage-selector
Add loadFixture test helper using mongoimport

Shelling out to mongoimport(1) is much faster than trying to do a bulk
insert from node. This can be used in tests to load up json files
produced by mongoexport(1).
Enable elasticsearch for travis builds
Fix running tests with elasticsearch
Add tests for model search interface

Model level testing for the elasticsearch integration. The setTimeout
call in the refreshElasticsearchIndex call is necessary because
elasticsearch gives an error about a missing index if you try to refresh
immediately.