Test with more modern rubies, bump runtime/development dependencies #8

Job	Run time
test (ubuntu, 2.7)	20s
test (ubuntu, 3.0)	6s
test (ubuntu, 3.1)	8s
test (ubuntu, 3.2)	12s
test (ubuntu, 3.3)	12s
test (ubuntu, truffleruby)	20s
test (ubuntu, truffleruby-head)	25s
test (macos, 2.7)	50s
test (macos, 3.0)	16s
test (macos, 3.1)	20s
test (macos, 3.2)	17s
test (macos, 3.3)	12s
test (macos, truffleruby)	37s
test (macos, truffleruby-head)	31s
	4m 46s

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