Support np.str_ dtype annotations, properly check tuple dtypes

[sneakers-the-rat]

Fix the other half of: #38

[coveralls]

Pull Request Test Coverage Report for Build 12325963960

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 6 of 6 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 98.302%

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Totals
Change from base Build 12325678030:	0.004%
Covered Lines:	1505
Relevant Lines:	1531

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💛 - Coveralls