Django-pg-bulk-update

Features
1. Added array_remove set function (by [roveil](https://github.com/roveil))

Bug fixes
1. Fixed issue with upper case field names https://github.com/M1hacka/django-pg-bulk-update/issues/46
2. Added deprecation warning and changed method names in BulkUpdateMixin due to django 2.2 method conflict (see https://github.com/M1hacka/django-pg-bulk-update/issues/44)

Refactoring
1. Redoing manager creation to new django style (https://github.com/M1hacka/django-pg-bulk-update/issues/45)

Features
1. Moved BulkUpdate methods from manager to QuerySet
2. Added ability to filter whole QuerySet in bulk_update

Bug fixes
1. Fixed issue https://github.com/M1hacka/django-pg-bulk-update/issues/41

Refactoring
1. Renamed BulkUpdateManagerMixin to BulkUpdateMixin
2. DefaultConnectionProxy replaced with TDatabase type

Features
1) Added IsNullClauseOperator

5) Reformated travis config:
* Removed python 3.3 from travis (limit exceeded)
* Removed postgresql 9.2 from travis (limit exceeded)

Bug fixes
1. Fixed issue https://github.com/M1hacka/django-pg-bulk-update/issues/36
2. Fixed issue https://github.com/M1hacka/django-pg-bulk-update/issues/32
3. Fixed parameter name for key_fields in bulk_update

Refactoring
1. Removed BulkUpdateQuerySet

Testing changes
1. Removed python 3.3 testing, added python 3.7
2. Removed postgresql 9.2 testing

Features
1. Added ability to return updated/inserted data with `returning` parameter

Bug fixes
1. Fixed issue https://github.com/M1hacka/django-pg-bulk-update/issues/23

Bug fixes
1. Fixed issue https://github.com/M1hacka/django-pg-bulk-update/issues/21