remove all the direct calls of np.random.*

[segasai]

218 incorrectly used np.random.directly instead of rstate

I've also added a test that will fail if it'll happen again.

[joshspeagle]

Excellent fix to both the tests and catching this bug, which would prevent full reproducibility.

[coveralls]

Pull Request Test Coverage Report for Build 919530575

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 77.113%

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Totals
Change from base Build 919359495:	0.0%
Covered Lines:	3595
Relevant Lines:	4662

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💛 - Coveralls