Django-postgres-copy

* Added `ignore_conflicts` option to `from_csv` method.

* Added Python 3.7 support

* Added ability to write to file-like objects

* Added `copy_to` options for `encoding`, `escape`, `quote` and `force_quote`.

* To realize speed gains, added new `ConstraintsManager` to drop all indexes and constraints on the database prior to loading.

* Added support for Django 2.0
* Dropped testing for Django versions prior to 1.11 and psycopg versions prior to 2.7.3, though they still likely work