Django-tailordev-biblio

- Add Django 2+ compatibility
- Add authors duplication cleanup form (22)

BC Breaks

- Drops compatibility with Django 1.7

- Make PMIDLoader & DOILoader bullet-proof

- Add PMIDLoader & DOILoader
- Add references importation view for admins (from PMIDs or DOIs)
- Better integrate the sandbox
- Make the sandbox deployable to Heroku

- Fix missing dev requirments

- Add support for python 3.4+
- Add support for Django 1.7+
- Switch to `py.test` test runner
- Remove jQuery implicit dependency

BC Breaks

- Drops compatibility with python 2.6
- Drops compatibility with Django < 1.7

- Add publication list partial template