Xrenner

Major new feature release:
* Python 3 compatibility
* Adds support for pluggable machine learning classifiers
* Multithreading - concurrent batch processing of multiple documents
* New model files:
* Added similar.tab to models for semantic similarity to OOV items
* Added nominalizations.tab for irregular verb nominalizations used in verbal antecedent matching
* Made all model files optional except `config.ini` and `coref_rules.tab`
* Support conllu input with multitoken units and virtual tokens from enhanced trees
* Added option to use sentence type (s_type) annotations (e.g. declarative, question, imperative)
* Added negated head and negated parent features (used e.g. to decrease coref likelihood for `didn't see [a dog]`)
* New DepEdit version with new operators
* New `utils/` folder with tools to create model files and classifiers
* Added a starter model `udx` as a building block for new models based on UD data

Direct import after installation now works as:
`from xrenner import Xrenner`

- Update for module importability in PyPI
- Minor improvement to ambiguous one-word person names

- Update for module importability in PyPI
- Minor improvement to ambiguous one-word person names

- Significant performance improvements
- New atomicity options using stop_list `` annotations (see documentation)
- Use_new_modifier_exceptions allows selective coreference despite prohibiting new modifiers
- Model improvements, refactors and bug fixes
- Restructured directories for PyPI deployment

- Significant performance improvements
- New atomicity options using stop_list `` annotations (see documentation)
- Use_new_modifier_exceptions allows selective coreference despite prohibiting new modifiers
- Model improvements, refactors and bug fixes
- Restructured directories for PyPI deployment, closes 41