documentation

[yxqd]

fixes #9

[coveralls]

Pull Request Test Coverage Report for Build 47

• 24 of 24 (100.0%) changed or added relevant lines in 2 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.5%) to 89.013%

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Files with Coverage Reduction	New Missed Lines	%
bem/diffraction.py	1	98.39%
bem/matter.py	2	77.78%

Totals
Change from base Build 31:	0.5%
Covered Lines:	397
Relevant Lines:	446

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💛 - Coveralls