tests

Update smoke tests to use both Rack 2 and 3 #136

Job	Run time
rspec (3.0)	38s
rubocop	15s
smoke_test (3.0, ~> 2)	30s
rspec (3.1)	37s
active_record_with_lock_adapter_rspec (3.0)	32s
rspec (3.2)	32s
smoke_test (3.0, ~> 3)	31s
active_record_with_lock_adapter_rspec (3.1)	39s
rspec (3.3)	32s
smoke_test (3.1, ~> 2)	35s
active_record_with_lock_adapter_rspec (3.2)	34s
smoke_test (3.1, ~> 3)	43s
active_record_with_lock_adapter_rspec (3.3)	34s
smoke_test (3.2, ~> 2)	39s
smoke_test (3.2, ~> 3)	43s
smoke_test (3.3, ~> 2)	35s
smoke_test (3.3, ~> 3)	37s
	9m 46s

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