(ElasticSearch 1.1) Support ES 1.1

* Scalar fields are now single-element arrays
* Removed "Related Content" search
* "Mapping Exists API" now returns empty object instead of error
(ElasticSearch 1.1) Remove manual install of ES 0.90 from .travis.yml
(Elasticsearch 1.1) Added better explanation about search document model
(ElasticSearch 1.1) Split _.extend operations into multiple statements
(Release 6.4.0) Bump version
(Release 6.4.0) Remove shrinkwrap
Using `delete` rather than `del` for DELETE rest endpoint

Express has deprecated the usage of `del`. All instances of using the
old method have been replaced.
Merge pull request #886 from mrvisser/elasticsearch-1.1

(ElasticSearch 1.1) Support ES 1.1
(SearchAccuracy) Don't index publicAlias
(Release 6.5.0) Bump version
(Release 6.5.0) Remove shrinkwrap
(Release 6.5.1) Bump version
(Release 6.5.1) Remove shrinkwrap
Email aggregation follow-up

 * 3 collectors for immediate, daily & weekly collections
 * various cleanup
Merge branch 'master' into emailaggregation

* master:
  (Release 6.5.1) Remove shrinkwrap
  (Release 6.5.1) Bump version
  (Release 6.5.0) Remove shrinkwrap
  (Release 6.5.0) Bump version
  (SearchAccuracy) Don't index publicAlias
  Using `delete` rather than `del` for DELETE rest endpoint
  (Release 6.4.0) Remove shrinkwrap
  (Release 6.4.0) Bump version
  (ElasticSearch 1.1) Split _.extend operations into multiple statements
  (Elasticsearch 1.1) Added better explanation about search document model
  (ElasticSearch 1.1) Remove manual install of ES 0.90 from .travis.yml
  (ElasticSearch 1.1) Support ES 1.1