Fix python 2 division issue in the Simpson integraton component

[bbrelje]

Porting Windows testing to appveyor revealed a problem with Python2 (failed 4 tests). Debugged and fixed the issue and now Appveyor is passing too.

[coveralls]

Pull Request Test Coverage Report for Build 17

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 24.062%

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Totals
Change from base Build 11:	0.03%
Covered Lines:	635
Relevant Lines:	2639

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💛 - Coveralls