Bump version to 0.3.0 (#336) #1507

Job	Run time
Wheel on macos-latest py-3.7	3m 55s
Wheel on ubuntu-latest py-3.7	4m 35s
Wheel on windows-latest py-3.7	4m 13s
Checks	1m 34s
Unit tests (macos-latest, 3.7)	8m 15s
Unit tests (ubuntu-latest, 3.7)	5m 5s
Unit tests (windows-latest, 3.7)	10m 1s
coverage	21m 23s
Run fuzz targets (macos-latest, 3.7)	43m 42s
Run fuzz targets (ubuntu-latest, 3.7)	33m 33s
	2h 16m 16s

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