[AppVeyor] simplify installation and execute all tests

[coveralls]

Pull Request Test Coverage Report for Build 218

• 11 of 11 (100.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.06%) to 73.636%

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Files with Coverage Reduction	New Missed Lines	%
spatialist/tests/conftest.py	1	90.91%
<!--	Total:	1		-->

Totals
Change from base Build 213:	-0.06%
Covered Lines:	1687
Relevant Lines:	2291

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💛 - Coveralls