Add support to Mongoid 9.0 #47

Job	Run time
Tests (2.7, csv_22.0, stable)	1m 3s
Tests (2.7, mongoid_8.0, stable)	1m 5s
Tests (2.7, mongoid_9.0, stable)	1m 2s
Tests (3.0, csv_22.0, stable)	42s
Tests (3.0, mongoid_8.0, stable)	42s
Tests (3.0, mongoid_9.0, stable)	43s
Tests (3.1, csv_22.0, stable)	41s
Tests (3.1, mongoid_8.0, stable)	48s
Tests (3.1, mongoid_9.0, stable)	41s
Tests (3.2, csv_22.0, stable)	46s
Tests (3.2, mongoid_8.0, stable)	48s
Tests (3.2, mongoid_9.0, stable)	42s
Tests (3.3, csv_22.0, stable)	49s
Tests (3.3, mongoid_8.0, stable)	46s
Tests (3.3, mongoid_9.0, stable)	42s
Tests (head, mongoid_edge, experimental)	1m 30s
Tests (2.7, csv_edge, experimental)	1m 5s
Tests (3.0, csv_edge, experimental)	40s
Tests (3.1, csv_edge, experimental)	46s
Tests (3.2, csv_edge, experimental)	48s
Tests (head, csv_edge, experimental)	1m 37s
Tests (2.7, mongoid_edge, experimental)	1m 3s
Tests (3.0, mongoid_edge, experimental)	46s
Tests (3.1, mongoid_edge, experimental)	42s
Tests (3.2, mongoid_edge, experimental)	47s
Tests (head, mongoid_edge, experimental)	1m 43s
Coverage	2s
	23m 29s

Provide feedback