update: arango dep for 8.1.7,<9

[aMahanna]

setting upper & lower bounds to python-arango to resolve #39

[coveralls]

Pull Request Test Coverage Report for Build 16445981820

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 94.779%

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Files with Coverage Reduction	New Missed Lines	%
arango_rdf/main.py	2	94.32%

Totals
Change from base Build 16196790579:	-0.2%
Covered Lines:	1071
Relevant Lines:	1130

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💛 - Coveralls