Xrenner

This is a maintenance release with updated requirements.txt

* bump depedit to 2.3.0 (with variable definition support, see https://corpling.uis.georgetown.edu/depedit/)
* python 3.8 compatibility (timing module)
* support flair 0.6.1 (version 0.4.5--0.6.1 APIs now supported, given sequence tagger model trained with appropriate version)
* add speaker compatible check for global 1st/2nd speaker coref consistency in input with gold speaker information
* expose sentence object to coref rules (e.g. `samesentence` / `!samesentence` constraints in a model's `coref_rules.tab`)
* added configuration options:
* `no_overlap` setting to allow/forbid nested markable coreference
* `force_single_type_chains` setting to enforce majority entity type in a mixed type chain
* bug fixes

Sequence labeler syntax now supports newer versions of flair too

* support flair 0.45
* support crf_suite-based sequence tagging (see `utils/train_crf.py`)
* new config.ini options
* sequencer_override_thresh - allows confidence threshold for sequencer entity classification to ignore KB
* default_atomic_named_entities - determines entity types in entities.tab which are assumed to be atomic (often places)
* max_suffix_length for substring based morphological entity type feature