Ipypublish

See [Bibliography Meta-data](https://ipypublish.readthedocs.io/en/latest/metadata_tags.htmlbibliography)

- Converted export configurations and templates from python to JSON
- Added validation schema for configurations and templates
- added option to control style of bibliography in latex
- Converted script executables to console entry points
- Updated test configuration from nose to pytest
- added many more tests for all export configurations and user interface
- fixed Mac Os build on Travis
- Improved user interface
- Added ipynb to python file (with commented metadata) exporter
- Updated documentation with new API and how to convert plugins

Raw output is now included in the latex (if raw format is latex), and html (if raw format is html)

and addition of documentation