Django-publications-bootstrap

- Drop usage of self-hoster six.py (See 17)
- Update initial data loading

- Merge PR [34](https://github.com/lucastheis/django-publications/pull/34) from source project

- Rename project from `django-publications` to `django-publications-bootstrap`
- Merge new features to `master`
- Use Bootstrap 4.0.0-alpha.6 for the layout

- Use Bootstrap 4.0.0-alpha.5 for the layout
- Refactor file inclusions
- Integration in project's base layout
- Rename person to author
- Add namespace for urls
- WIP update tests
- Update and extend models
* Renamed `List.list` to `List.title`
* Renamed `Type.type` to `Type.title`
* Publication
- New NullCharField to support nullable but unique CharFields (Fix for Django<1.11)
- Updated fields:
+ `citekey ` is unique
+ `doi` is unique
+ `isbn` is unique
+ `volume` is CharField
+ issue `number` is CharField
- Added new fields, to support references to be cited in common formats like ACM or IEEE:
+ editor
+ edition
+ school
+ organization
+ location
+ country (requires django-counties)
+ series
+ volume
+ number
+ chapter
+ section
+ status
- Updated admin layout
- Updated Bibtex import to support new fields
- (Partially) updated export formats to support new fields

- Minor bug fixes
- Added migrations
- Allow non-numerical page entries
- Fixed compatibility issues with Django 1.9

- Added support for Zotero/unAPI
- Added support for Endnote/RIS
- Bug fixes in BibTex parsing and rendering
- Improved performance
- Dropped support for Django 1.4