Adjust 3.3 to elasticsearch 1.0
This will *not* run on 0.9!
Add existing articles to set via API (fixes #130)
Merge branch 'hotfix_elastic1.0' into release-3.3
Merge branch 'release-3.3'

Conflicts:
	.travis.yml
	amcat/models/article.py
	amcat/tools/amcates.py